Ok I know a lot recommend going with a 750 PSU for xfire / sli .
I have a Corsair 620HX http://www.newegg.com/Product/Product.aspx?Item=N82E168... I know it only has the 2 6+2 pin cables for 1 GPU. Corsair has sent me 2 cables that are a 6 pin @ one end that plugs into the PSU and it splits off into 2 6+2 pins, so now I have 4 6+2 pciE ends to hook into 2 GPUs.
Your system is going to need a fair amount of power! These supplies should work well for you.
HX620W - One of the world's most awarded PSUs, the HX620W has modular flat black cables, a quiet fan, and enough power to run just about anything. SLI and Crossfire certification for all the serious system builders out there who demand quality and power.
TX650W - The TX650W is a powerhouse featuring excellent efficiency and a near silent 120mm fan. Upgraded industrial grade components provide clean power throughout its 5 year warranty. Nvidia SLI certified and compatible with all dual-GPU configurations.
TX750W - With four 6+2 PCI-Express cables, the TX750W has the juice to run even the most power hungry system. A single, quiet, 140mm fan and industrial grade components would make this PSU stand out above most of the competition, but fully sleeved cables, a five year warranty and an excellent price point puts it well above the rest.
HX750W - With modular cables and enough power for demanding dual-graphics card PCs, the Corsair Professional Series HX750W delivers up to 750W of power with up to 90% efficiency and at whisper-quiet sound levels.
Now that’s with the CPU OC but without the GPUs OC so if I get the GPUs @ stock 850 speed I should be ok no? or am I missing something. I know I will be pushing the PSU and if its poops out oh well I will get a 750 then. Thanks