Great write up, and I'm glad to see that you understand the value in having these files accessible at any time. I have a similar setup. I use 2 120 gig drives for the main files and 2 USB 2.0 external drives for the backups. The server and MP3's are available to every room via gigabit Ethernet or 802.11g. The server also has an audio feed to my audio closet where my whole-house audio amp is. So I can set up a playlist on the server and hear it in all rooms and the deck and garage. It is definitely my favorite part of my house... the music all over the place.
Another cool feature is integrating it with HAL automation and voice control. I can pick up the phone and say "play Ozzy on the deck", and immediately it starts playing. It will also wake you up with your favorite MP3s's or they can be triggered by events. The software is dirt cheap and allows total integration with your MP3 collection. Have you messed around with that yet?
Again, good summary and I am sure it will help some folks who have been considering a total MP3 system for their home.
