I've been looking into this lately also. I'd like to use an IR/RF remote for my different zones, but it seems most manufacturers are lagging in this area. Remote wired IR sensors or wired remote volume controls which turn off the speakers at the minimum setting seem to be the norm. How low tech. You would think that something like this would be in demand and fairly inexpensive.
Anyway, I have come across a few products that do offer remote speaker switching. Considering that I already have a couple of spare amps, none of these are really ideal for my situation, but maybe for someone else these might just be the ticket.
First is the Xantech that has already been mentioned. Unless there is some way of getting away without having to buy the remote programmer, this costs way too much IMHO.
Xantech
Next up the Marantz ZS5300 multi-zone amp. This, for me, is the most promising solution. While it won't allow me to use my current spare amps, the price is not too bad considering you get 6 channels of amplification and a remote.
Marantz ZS5300
There are numerous receivers & integrateds with remote speaker switching and/or multi zone capability. Here are a couple that have caught my eye. If your on the cheap it's hard to beat the Sherwood, and I've seen the Denon on E-cost for less than $200 in the past.
Denon DRA395
Sherwood RX-4105
If anyone knows of any other options throw 'em out.
-Dave