I have and UltraLite and a scarlett 18i8 think they are both great.
Scarlett to drive into and iPad and the UltraLite because it is 24/128 and powers of the firewire… one less adapter traveling…
I would like to suggest the Roland Octa-Capture or Studio-Capture interfaces. They are substantially less expensive than Apogee, RME, etc., but appear to have good converters and very low latency. The Octa-Capture is 8in, 8out; the Studio-Capture is 16in, 10out.
Two features make these devices particularly useful for your purposes:
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you can use either of them as a mixer without the computer connected at all. It’s kind of fiddly to do so, but it’s possible.
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if you need more channels, you can add a second identical device and treat the two of them together as a single audio interface with lots of I/O.
I am heading towards an Antelope ORION 32… I don’t mind spending more if you get more…
I’ve been really exploring mixer v interface over the last couple of weeks. Ran up a 24 ch soundcraft with all my Elektron/modular/Op-1/Virus etc. bussing everything to everything.
Did the same with a Yamaha LS-9 which was cool b’cos it gave me 4 fx & dynamics + I could sidechain.
In spite of the power I felt like I was at work mixing with the focus now on the desk & not my musical endeavours.
Once I had a patch I really liked I transferred it back to my RME UFX just running 12 in to 8 out. I’ve got to say I’m a lot happier this way as it’s more transparent & the focus is back on the machines. I can still record everything separately or bussed thru the OT. Best of both Worlds for me 
I would stil wait a bit and would go for one which supports Dante Protoccol like planett 88 from esi http://www.esi-audio.com/
^ funnily enough saw the Richie Hawtin interview posted here last week & he uses an LS-9 with Dante cards!