Go out and buy an inexpensive second receiver or integrated amp. Then connect an extra tape loop output from your main receiver to the second receiver. Connect the multi-room system to it, and then use the Record out feature of your main receiver to control the source.

An added bonus to this is it will allow you to watch a movie in full surround, and let others listen to a CD in the remote rooms.

You don't need to spend a lot of money on this piece...just get a basic unit (even an older used one will often fit the bill)

In many cases, I have used the old surround receiver for this when I have upgraded my clients system. The client can then still use the gear they have, but get the new technology they desire.

Any questions, let me know...Derek