Try a Squeezebox from Slim Devices. You can use either lossless (WAV, FLAC, AIFF) or lossy (MP3, AAC) music formats, and the sound quality can range from decent using the unit's analog outs to excellent if you use the digital out with an external DAC. A high powered PC is not required for this, but lots of disc space is mandatory if you choose to use lossless formats.
Making a PC into a digital CD Jukebox
I am thinking about getting a high end PC and using it like a CD jukebox. My plan would be to get a fast PC with LOTS of disk space and memory, then rip all my CD to disk. This way, I'd be able to create play lists using Real or something like it. I would connect the PC's audio output into my receiver's CD or AUX input. My question is - is the sound card in the PC capable of producing reasonably high quality sound reproduction? I'm not an audiophile, but I do want to make sure I'm not taking a step down from a regular CD changer.