Thanks for the reply. It looks like I only have about 75 watts to play around with, having everything at max load. Would having both the CPU at 4.4ghz, and overclocking the 2 570's throw me over the max? Luckily I have a quality brand PSU on my side. . .
Gaming load total system overclocked I7 LGA1366 556watts with 2 x GTX570 in SLI (from my link) don't look at the Furmark load which is nothing you see in normal use! You have plenty left for overclock!
Remember that all power numbers are given at the wall, assuming the power supply they tested with was 90% efficient at that load(it was likely less), that 773 W at the wall is only 0.9*773 = 695 W from the power supply itself, and as rolli said, that is an unrealistic worst case scenario you will never see so you have plenty of head room left over.
The 1kW units are for people who over estimate and just want it to have it, the HX 850 will handle any dual GPU setup just fine.