We’ve been using Sonos for years. In my opinion it’s the best whole house audio system that I’ve ever used and I’ve tried a number of them. (And it’s designed by a startup)
Last year, our Sonos experience became even better when they came out with a new touch remote and an iPhone app. With a touch of a button I have last.fm, rhapsody and our local music library streaming in multiple rooms of our house. We had been using Sonos in three rooms of our house plus the patio.
The pre-requisite with Sonos is that you need speakers in every room where you want audio. Any type of speakers will do. But sometimes setting up speakers is a hassle. Putting two speakers in ideal locations isn’t always convenient so that’s why some of our rooms aren’t available to our Sonos.
That was until I bought the Sonos S5 
last week. The S5 is a single amp/speaker system. Plug it in, press a button and it automatically joins your Sonos music network. It just works. I think the audio quality is excellent for an average size room.
I’m so happy with the S5 that I’m absolutely going to get a few more.