Are there any high quality speaker systems that rely on wireless to deliver the signal? I know that is potentially contradictory, but I would sacrifice a bit of quality for the convience of no wires.
I've got a friend who uses the Sony 900MHz Wireless Speaker system (http://www.smarthome.com/8214.html). It's a little expensive, but not bad, I suppose. He doesn't feel he's had to sacrifice sound quality for the convenience of wireless at all.
Not sure what the wattage is on them, but one reason we got them is that they're good up to about 80' and the frequency doesn't interfer with portable phones which the last ones we had did!