Here's my system:
Gentoo
Amarok 1.4.0
USB reciever - using 2 channel stereo
Alsa drivers

I've used Audacious and Banshee. I just tried Amarok. The sound quality is really bad because the bass and trebles frequencies sound really weak(this is with the EQ on). When compared to Audacious and Banshee, I don't have this problem(I use the EQ on them also). I can get 4 times more strength in the all the freq. in the other players. I like Amarok and I would like it to become my main player, but sound qaulity is the most important thing.

I've heard really good things about the Xine sound engine, perhaps the development for Xine engine with USB audio is neglected?

i'm open to suggestions if anyones got any

I've heard really good things about the Xine sound engine, perhaps the development for Xine engine with USB audio is neglected?

You are aware that there is a difference between xine (decoding of media files) and a audio card driver?

I think that sound quality has nothing to do with the amount of tremble or bass you can add to the audio signal.
I guess you want to start to "improve" the equalizer in Amarok. Get the code and work on it, certainly other people will appreciate your efforts.