[Gogar]

If your music is iTunes/etc. driven you could consider getting a few Airport Express devices and you can individually select each device and it's volume from your phone/ipad. $89 each. You would need a seperate power amp or receiver for each 'zone' though.

I have 3 computers on my wifi and 2 airport express(es), for a total of 5 "zones" that I can control via my phone from anywhere in the house. It's like Sonos on the cheap, sort of.