Holy crap, I just measured the rig at 1100 watts total with my new meter! Each card is drawing roughly 320 watts, so you're right on the mark. I've been pushing that corsair 850W supply pretty hard... I'm actually amazed it has worked this well. Surprisingly, the supply feels cool to the touch and the fan is barely spinning. Might be time for a higher-wattage supply or some other setup to split the load.

Yeah these cards draw a surprising amount of current. I have 4 in each rig, 3 cards and the mobo hooked up to a 1300 Watt PSU and the 4th card hooked up to a 600 Watt. PSUs actually run more efficient when they are not pushed to the max.