If you have a usable zone2 or zone3, then the solutions below are overkill. Otherwise...
I don't know much about Sonos (apart from the price) so I cannot say much. The two solutions with which I am familiar (i.e. using) involve a PC.
The first variation makes sense if you already own an iPhone or iTouch or would like to justify buying one!
1. PC + iTunes (Wi-Fi remote controlled by iPhone) + as many 100$ AirPort express (which then serves as "remote speakers") as you have receivers in your home.
2. PC + SqueezeBox duet (which comes with a Wi-Fi remote + player) + as many 200$ remote player you have receivers.
Solution 1 is a bit less user friendly (because of Apple's strange notion of what a useful remote control is), but is about 50% less expensive.
