You should definitely dig into software modular if you like synthesis.
I recommend Nord Modular G2 Demo which is free and that you can use as a monophonic midi sound source, it doesn’t have all the modules of the real hardware but will give you a good glimpse.
Wow. Thanks for all the replies and info everyone. This will be a lot to dig through. Unfortunately I don’t own an ipad or else I’d be very interested in checking out the Moog app. Maybe down the road.
I think Reaktor Blocks is in the lead. I like the idea of it easily integrating with real hardware as well. Hopefully they will keep adding modules.
Forgot about Madrona! Will download the demos.
I do have Ableton Suite, and therefore max4live. Might give Oscillot a go as well.
Thanks again everyone, demos and research should keep me busy for quite a while, and might even help to quell some GAS for hardware. 
Reaktor obviously covers it all…
You could have a little play with the Nord G2 demo also, some things are disabled but you can explore and make some great patches…
http://www.nordkeyboards.com/downloads/legacy/nord-modular-g2
Sorry missed the earlier tip from @gauthier
Reaktor Blocks really is hard (impossible?) to beat
a few +1s:
Pulsar Modular (if you have a Mac) , really sounds great.
Softube Modular, sounds great… a ‘eurorack’ clone, can get expensive, once you add intellijel modules (and other future ones)
Axoloti , for 65 Euro for the hardware, so you can use standalone , fun.
Oscillot , its ok, but it didn’t do anything for me… oscillators/filters I didnt think had much ‘character’ to them… but perhaps I didn’t invest enough time into it.
BEAP w/ Max, great if you want to also dive into Max.
a real ‘curve’ ball, checkout encoderaudio.com , not really modular, but buchla/experimental inspired M4L stuff.
I think the only issue with software, is it probably lacks the physical interaction side , that I think many enjoy with Eurorack. Its not really cured me of the Eurorack desire.
in fact im backing AE Modular which I hope will let me get a better feel for modular, at a fairly cheap price.
Native Instruments doesn’t really need to develop their own modules for Reaktor. I’d strongly recommend checking out the Reaktor User Library and the decade+ archive of options there. I’ve long since given up trying to stay current on all the user Blocks, as there are some really creative people dropping new Blocks every day.
I wanted to hit modular about 10 years ago but after realising the amount of multis I’d need I decided to get the Nord G2 Engine instead to satisfy my experimental urges.
Was very happy, especially since you could have as many cables plugged into a vsocket as cpu allowed…
Finally went hard-modular this year due entirely to MI Braids and Clouds.
Now it’s an EP360 with little spare room!
Reaktor Blocks FTW! Only downside is high CPU usage on more advanced configurations.
reaktor w/ blocks is an amazing deal. cause you still get reaktor. and there are tons of free synths and effects and more… plus lots of free modules for blocks…
AAS Tassman
I’d strongly recommend checking out the Reaktor User Library and the decade+ archive of options there. I’ve long since given up trying to stay current on all the user Blocks, as there are some really creative people dropping new Blocks every day.
Good to know. Thanks. Can’t wait to explore these. Sounds like I’m going to be busy diving into Reaktor over the break.
Thanks everyone for the input! Keep the suggestions coming for other readers of this topic, but for me, personally I think Reaktor Blocks will fit the bill nicely. Thanks again!
Finally went hard-modular this year due entirely to MI Braids and Clouds.
Now it’s an EP360 with little spare room!
Yeah, that MI stuff is what is tempting me. Clouds, Rings, Braids. Love the sounds coming out of those little bastards. r beny on YouTube is doing incredible things with some MI modules.
Loving this one at the moment:
Reaktor is great on flexibility, price, and extensive library, but softube modular sounds way better imho. Both tend towards CPU hoggery, especially at higher sample rates. If I had to pick one only it’d be Softube though, something about the sound and feel really appeals to me. Could do with some more sequencing options, though.
I’m in the same boat. Will order within the next weeks. Can’t resist. Braids and Rings and some other stuff.
tassman is really nice sounding but is in terrible need of an update. the patcher window is a nightmare. the whole thing needs an overhaul. hopefully in 2017 that’ll happen but it’s been 10 years since it’s had a real update. it got an update to make it 64 bit friendly but beyond that i’d avoid it.
Softube modular is probably the closest you will get to the real thing and also boasts three expansions as well as an additional drum expansion (Heartbeat), which you have to purchase separately though.
These are also all available in softubes new subscription service called Volume One which includes 16 Softube plugins all bundled together for $19.99 per month.
I recently took the time to practice and explore Arturia Modular V3 in the V collection 5. Wow this thing can get some good Moog tones and then some. The biggest upgrade is the ability to increase the UI to 200% so you have better zooming. CPU hit isn’t much.
When any modular software you can pickup a lot of good youtube tutorials and just explore. Once you have the concepts down you can just grab any other software modular and design sounds and sequences.
I still haven’t upgraded to Reaktor 6 because I’m waiting for what komplete 12 ultimate offers. Maybe Battery 5 could turn into a Geist program. Even though it’s software I still save the loops I designed that day because at times it’s hard to patch it again to sound like how I felt when I wrote the patch. I still won’t give into the Eurocrack though.
Reaktor is pretty much the king here, but Softube modular is a lot of fun and sounds great too. I also like how they’re integrating their other products as modules to it as well. Heartbeat is a great example, but also some of the FX are available too. It’s well worth trying the demos available.
My biggest issue with it is the CPU usage can get quite heavy quickly, so be prepared to bounce it down to audio and/or not expect to run a lot else simultaneously with it. I have a very well spec’d and overclocked i7 6700K build and it still can be very burdensome on large patches.
Check KVR for people selling it (or any other software you want). Was pretty easy for me to find it for $50 incl. iLok transfer fee. KVR is a great resource for people selling software. I get some massive deals there (never pay more than 50% of original price and usually more like 25-40%)
There’s nothing like real modular.
Software is simulation, but all behaviour is programmed.
20+ years into this now, I’m so past all the hardware vs. software and analog vs. digital. It’s all just tools and stuff to make fun noises with, so use what makes you happy and let others enjoy what they want to. I suck just as badly with the hardware I own as the software. 
For anyone considering Reaktor 6, I made a large collection of free Blocks called “Euro Reakt”: https://www.native-instruments.com/en/reaktor-community/reaktor-user-library/entry/show/9093/
I’m hoping to release an update in the next week or so.
I’m a big Reaktor fan due to how well it integrates with everything. It can act as a standalone or a plugin in all major formats on Windows and Mac. It can natively receive MIDI and/or OSC, plus mapping it to a controller is a matter of right-clicking a knob and using the MIDI Learn function. The Blocks Library is diverse and the standard Blocks are insanely good (especially with all of the free expansions!). My biggest Reaktor complaints are:
My next favorite is Audulus, which I’ve only recently picked up on Mac. I haven’t purchased the iOS version yet, but will do so soon. The sound quality is excellent, the factory presets are incredible, and the creators are very active in the community. I really like that they have a one-stop forum post for downloading all user content at once (http://forum.audulus.com/discussion/969/forum-patch-repository-updated-72117/p1).
I had a Nord Modular but sold it due to how much I had to juggle just to get it working. Sometimes the editor would run correctly, sometimes not. I ended up needing way to many cables to use it, so it always felt separate from the rest of my workflow. I loved the sound quality, though. It definitely has a mid-90’s/early 00’s IDM vibe (probably because it was used on so many of those records!) that isn’t present in a lot of modern stuff. Yes, it’s hardware, but there’s a free demo that works perfectly (http://www.nordkeyboards.com/downloads/legacy/nord-modular-g2). There are hacked versions on Electro-Music that unlock all of the features, and there are versions of both the editor and the demo that have been tweaked to run on modern operating systems (there’s a MacOS version that is packaged in WINE).
The Axoloti is very cool, but it still feels like a work-in-progress. My biggest hang-up with it is the documentation. A lot of the modules have unhelpful, one-liner documentation. Also, many of the modules have weird acronyms on their ports, so it’s difficult to determine what the functionality of the port is. The User Library is massive though, even just off the power of SirSickSik’s contributions (http://community.axoloti.com/t/sirsicksik-contributions/1731). Once it all comes together, it might be the best around. I suppose it’s not a pure software modular, though, but the cost makes it very accessible to everyone. If you are handy with a soldering iron, I think the AxoControl is an essential part of the Axoloti experience (https://www.thonk.co.uk/shop/mtm-axocontrol-pcb-baseplate/).
Softube Modular feels the most like a hardware modular, but the module selection is limited and focused more on subtractive strategies. The sound quality and workflow is very nice, and I sold my hardware 4ms SMR a few hours after demoing the Softube version. Aside from the module selection, I’m not a fan of the copy-protection (iLok and/or Gobbler).
On Windows, WREN is very promising (http://bluehell.electro-music.com/wren/). The workflow is nearly identical to the Nord Modular. Everything is well-documented (http://bluehell.electro-music.com/wren/modules.html). I previously had issues with it interacting with my audio interface, but I should check it out again.
OSCiLLOT is absolutely worth checking out if you’re already part of the Live and Max For Live ecosystem.
For PureData, Automatonism (https://www.automatonism.com/the-software/) is a lot of fun. My only issue with it is that it has a very specific way of saving and loading patches, so I’ve had to spend time renaming/restructuring my file path after incorrectly saving patches.