I use X-10's Wireless Sound Power Kit
http://www.x-10.comIt's 10 Watts RMS x2 which isn't a ton of power
but most wireless systems will be somewhat limited.
They transmit on 2.4 Ghz with adjustable "channels"
Works very well... See my post titled...
"Not Impressed with my X-10 Wireless Surround"
I was a bit premature in my assumptions!