I have tried several guitars through my system (including my bass). I used an interface (M-Audio Black Box - no longer sold). The biggest problem is playing with any processing on. There is always a delay (even when playing stereo). I hit a chord and hear it a half second later. Not cool.

I was able to use the "Pure Audio" mode on my Onkyo receiver (bypasses all the processing). Doing this I got just the mains (no sub), but it did sound cool.

Dave
Audyssey Setup Guide