Playing mp3's through high end audio equipment is not going to make them sound better. Had a client who wanted to listen to mp3's he downloaded off the web throught his DCS dac, Mark Levinson amp & pre, and Thiel speakers. We installed a device with a hard drive that would allow him to transfer files from his computer (about $5000). He was so disappointed with the sound that he he tried to return the unit (could not return it - we tried to talk him out of it before he purchased it). In my own experience, I find that the higher the level of resolution of audio equipment, the more you are going to hear the flaws in the recording format. While mp3's might sound almost as good as cd's on inexpensive computer speakers or portable mp3 players, when you use high end gear they sound about as good as the fm radio in a boom box (320kps). And if you use higher compression the quality goes down hill quick.
BTW - I have a sound blaster audigy2, monarchy audio SM70 class a amp, b&w lm monitors, ps audio ultimate outlet, and kef sub hooked up to my computer.