Soundcard with preamp section

What's a good soundcard for 2 channel audio? should i go for an external one so that interference from the computer is limited, i've heard that the external sound cards suffer from problems with power over usb. I was thinking of getting some kind of m-audio card that has a preamp box outside the computer, that way i can ditch the preamp stage of my integrated NAD C352 amp.

My mp3s are mostly 44.1khz / 192kbit

Current System
Foobar2000 mp3 software
VIA AC97 Onboard sound chip
NAD C352 Integrated Amp
Mission M34 Floor standers
Monster cables

I am also pondering the purchase of a Crown XLS 402A to replace the NAD C352

ALSO

Has anyone used a sound card (or similar) pluged straight into a power amp?

Cheers
Mike