I don’t have an A4, but I do have the following setup with a 4+:

Connected to USB host via a hub:
[ul]
[li]DSI Tempest[/li]
[li]Nord Lead 4[/li]
[li]Access Virus TI2 Desktop[/li]
[li]Moog Slim Phatty[/li]
[li]Moog Minitaur[/li]
[li]Arturia KeyLab 25 as a midi controller[/li]
[/ul]

Connected via straight USB:
[ul]
[li]Macbook Pro[/li]
[/ul]

Connected via DIN:
[ul]
[li]Octatrack[/li]
[li]DSI Prophet 08[/li]
[li]Nord Micro Modular[/li]
[li]Akai Midi Controller[/li]
[/ul]

I also have an Ableton Push and Maschine Studio hooked up directly to the Mac via an different USB hub.

I gotta say, I frickin love the 4+. Originally I bypassed the Mac and had everything driven by the sequencer on the Octatrack, and I didn’t need any filtering, but I’ve since moved a little bit back ITB and have set up a bunch of filtering and port remapping.

The 4+ is so flexible, it’s insane. I have each hardware device listening on Ch 1, just to keep things simple, but on the 4+ I have a bunch of port remapping so I can select a different MIDI Channel on one of the controllers and it will only go to the specific synth. In Ableton, I just created a bunch of External Instruments mapping to the 4+ port on Ch.1 so those are very easy to add to a session and get up and running.

The only filtering I’ve done so far is to filter out program changes and CC events on each of the synths for each of the other synths (if that makes sense). Basically what was happening was that I’d change a preset on one synth, and it would change the preset on all of the others.

Haven’t done much with snapshots or MIDI over Ethernet though.

It’s pretty sweet, and very easy to configure. Have fun!