I have a MAC Mini with an external 2TB Firewire drive that I'm using for a music server.
I have been running iTunes and listening to music, using my iPad as a "remote" with the app. I also stream with 3 different AppleTVs to different locations in the house. I have the Mac Mini in my home theater in the basement.
I recently downloaded Channel D's PureMusic on the 15 day trial deal. I'm quite shocked at the difference in the quality of the music played when using this software. It is shockingly good, and it costs just $129. It even improves my audio playback through HDMI, into my home theater processor.
If you aren't already using a software like this, you seriously need to, at least, give this the free trial.
I bought it.