if you're not using multiple programs at the same time (like some of us for audio-processing), you should be fine with a simple stereo or 2.1 usb-card. what kind of chip is being used for the on-board sound? most-on-board soundcards aren't that great when it comes to sound-quality. I'd do some more reading (yes, I know, there's lots of info and it can be hard to take it all in
). I'd search for the projects durwiid and Red GTi VR6 are on.... Those two have done some great contributions when it comes to audio and audio-processing.