I wanted to have music/radio in all the rooms upstairs in my house, but it normally costs a fortune for multi room audio kit! So I decided with the help of a Pi and a plaster board saw to do it myself!
The Pi itself runs raspbmc, its connected wirelessly to my main samba server so it can play flac/mp3s, it can also get digital radio via a TVheadend virtual machines running on the same server. Also shoutcast from another vm when I get around to it. The amps are 4 X Lepai lp-808's, they where very cheap at £9.99 each nevertheless are more then powerful enough to drive the 4 X 6.5inch 100Watt ceiling speakers I bought @ £40. As its only background music I was looking to have (and to cut down on costs) there is only one speaker per room, but trust me they are more the adequate to fill the entire 1st floor with lovely music. Having 4 amps allows me to isolate the rooms easily. I may add some gpio via web control depending on how we use it. As the Pi is headless we are using the XBMC Yatse android app to choose what we listen to. The amps are powered via an old atx power supply. Please excuse the untidiness of it, its all going neatly into a cupboard when the rooms decorated.
Thanks again
Barry