What's the difference between the SB Live! and the Audiology NX (both USB 2.0) other than the extra 2 channels and $100 (AUD)? I'll be wiring the sound card up using 3 headphone to 2 RCA jacks to run short RCA leads direct to my amps in the car. This will all be running of a tablet PC which will also serve as a touchscreen at the front of the car.
Also, are there any comparable USB soundcars other than the M-Audio Sonica (probably too expensive)? I also had a look at the Zalman RSSC but i think creative would be better.