Well there are a lot of vaibales and some miss information being passed here... You say you want the BEST sound but for MP3's... If you want the best sound stick with WAV's or lossless compresssion... I use APE files for my compression and Media Jukebox (now media Centre) which has built in ASIO connections to bypass the awful windows KMangler.
Secondly you say the BEST... You realize pro cards can be >2k for a soundcard ?? if you want nearly the best RME / LynxTwo / Etc range from about 300 to 1k or so... If you want consumer (midfi) the M-Audio Revo and 410 or 24/96 are still miles ahead of the SBLive / creative cards but are not in the same class as the others listed above...
Sorry Witchdoctor but
1) Use the M-Audiophile Soundcard
2) run the digital out from the card into an audiophile dac
3) run the analog cables from the DAC into your pre-amp.
4) Use very good cables.
5) try experimenting with DFX , a plug in for musicmatch jukebox
is pretty much all incorrect advice...
1) As addressed above.. Good but midfi (still better than most consumer recievers to be sure)...
2) The point of using studio cards is that they have exceptionally good DACS for the price point involved... The Revo DAC's (IIRC) have better performance specs than the Lexicon processors... The point here is using the soundcard DAC's...
3) as above
4) granted but speaker cables is all he should need..
5) Hmmm... are we trying to get accurate sound here or are we looking for enjoyable coloration or distortion ??? I agree that a correct implementation of CSII is worthwhile as I am a 5.1 user and enjoy 5.1 listening of 2ch audio... DFX or other ambience filters do do it for me personally... Also MusicMatch makes me shudder... it has no ASIO output method (I think) and as such ALL sound passes through the KMixer and gets bit mangled very audiably (play a DTS CD to test)... Media Jukebox in ASIO mode or WinAmp with the ASIO plug in is reccomended....
For a recent High end ABX card review including Lex MC12 for reference and a 6K DAC check This link...
http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=236215&
There are many other such shoot outs including Theta equipment and other high end gear brought down to size... It is expected that this year will see a M-Audio 1010 replacement with uprated DAC's and hopefully the consumer drivers of the Revo including CSII and the speaker delay / bass management of the M-Audio's new consumer division (the Revo is thier first product release)... This will be a outboard solution with multiple in / outs like the 1010 if hints are correct... This product will proably tempt me if in the 3 - 500 range...