Modern House Audio Setup and Control over Ethernet

My music environment has changed in the past several years. With itunes I can organize music into playlists and quickly access what I want. I like to see information about the music as it plays, and when I listen to internet radio and I frequently use google to learn more about a group I'm not familiar if I hear something I like.

I was recently asked to do the low-voltage wiring for a multimillion dollar house that was being rebuilt for resale. I had to decide what wires to run. It was easy to decide to use cat 6 for phone and/or data, and rg-6 for video. But did I also need speaker wire? It was possible to send sound over ethernet. Since there were a number of good locations for audio equipment, it was not clear where to string home-runs of speaker wire. It was not even clear where the speakers should go; it would depend on the furniture arrangement. Also, I've never been totally happy with in-wall speaker quality and they never seem to be in the right position.

So I decided not to run speaker wire. Just plenty of good ethernet wire.

Well the ethernet is in and working, the walls are sheetrocked and plastered, the trim is in. But now what? How do I actually deliver good sound over ethernet? These notes contain an explanation of how to use an ethernet network to deliver high-quality audio from multiple sources to multiple locations to provide a state-of-the-art interactive audio environment.