What kind of usb card would you suggest
I heard the Tascam US-122 works very well (AFAIR it has a ALSA module of
its own). I run an Edirol UA-25 which works very nicely out of the box
using the ans_usb_audio module.
Please note that both cards don't offer software controls via alsamixer,
both have hardware controls for all settings.
Best regards
ce