Re: GPU & PSU upgrade!
The 550W Corsair will perform as well, or better than the OCZ. And the 750W is a big psu. I run dual cards on a 700W psu. I had a 520W Corsair but needed more pci-e cables.
Depending on you upgrade plans.. realistic plans, the 750 would only be if you planned xfire cards. I'd spend the extra on the 550vx over the OCZ.
Again, only my opinion, and you should get more than mine.
Foldie = i7 950@ 4.0Ghz Gigabyte x58a-ud3r EVGA 970 SC Corsair H100 Corsair hx520 3x2gb OCZ Gold Corsair 650D
Woohoo = L5639 @3.1Ghz EVGA SR-2 gtx 260-216 Hyper 212+ Corsair 1050hx 6x2gb Corsair XMS3 Blackhawk Ulra
Alienware 18 - SLI 770M 4700mq 16Gig