Craig,
I am not sure about other speakers but for Wet Sounds.
We have had really great luck powering a pair of PRO 485's with the following.
Massive Audio P800.4 (4 ch in 2 ch mode) will put out 400x2 at 4 ohms.
Arc Audio FD 4150 (4 ch in 2 ch mode) will put out 320x2
I prefer to run the towers like this because you are running a lot of power but at 4 ohms.
Tim
www.wetsounds.com