Zargon,
Thanks for posting the killawatt info. That's the point at which I didn't want to speak to, because I don't have a killawatt (yet) to measure actual load.
I have 2 x 7950 running in a rig on a killawatt
its showing ~550W pulled from the wall
a 650 *should* be fine
I have a 1kw on it though because its what I had
and I couldnt shoehorn the 6870 I have into due to mounting issues