Intel and Nvidia GPUs are your safest bet for Linux support.
On a side note, have you ever tried FL Studio? It runs
great on Linux with the WineASIO drivers and a realtime kernel.
I made a drumstep tune with it last year to get a feel for it and I really liked it. Not used it since though.
I have, it's a pretty nifty program, but again, I prefer to compose on my Amiga via OctaMED S.S., MIDI, and real hardware.
Here's what I've got:
Kaossilator I, Kaos Pad 3, MicroKorg, Tascam DR-07, Akai XR-20 Drum Machine, ART Tube MP Microphone Preamp (Model 127), Mic with Mic Stand, and a few other odds and ends like a lap harp and such. Oh, and let's not forget the A1200 with 80Mhz 060!