I think your best bet would be to ditch the typical 'PC' sub/sat combo and get a proper 2 (or even 5+) system up and running, you can then (check my sig) connect your card digitally to the receiver pretty much bypassing all the parts in the sound card. Connect all drives digitally to the card (or through the ide would be best) So your machine is basically just chucking out a digital signal (all the quality comes in the conversion which is handled by your quality external equipment) Get a big HD, ditch mp3's and just use .WAV A 44,100 16bit wav file will stay digital all the way to the 2 channel rig and be converted by the DAC in the receiver giving you CD quality audio. If you can't place the 2 channel setup equidistant in front of the PC (which most can't) and imaging is important get a quality set of headphones and run them from the 2 channel rig. All this is expensive but you'll never go back to the typical setup.
Hope that helps.