I second Haoleb. MP3s are not of sufficient quality to justify buying a nice stereo system to play them. Granted, they will sound better on a nice stereo than through computer speakers, but still...

On that note, I often play songs from my iPod over my home stereo. It does sound MUCH better than playing MP3s through my decent computer speakers, but I didn't by the stereo to play MP3s. It's just a fringe benefit.