a Speaker switchboard for Halloween

Ragtop

I just got Sparkfun's MP3 trigger that I am going to pair up with an amp. I would like to have a switchboard from the amp to the speakers to make the sounds come out of specific speakers.

Has anybody done anything like this before? I am using the propeller chip.

Ragtop

I was thinking of using Optoisolators on the control line of each speaker. The amp is a chinese 12vdc 500w.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&rt=nc&nma=true&item=320697743552&si=fP6x9sfuTcvxV0N5VWbCETP4gCA%253D&viewitem=&sspagename=STRK%3AMEWNX%3AIT

Super cheap, so I don't have hopes for it.