I'd go with the OZC = the reason i posted the link. Btw i own a Corsair and two OZC units. Haven't had an issue with any of them. The OZC ZS is better quality then Corsair Builder series imho.
For a system using a single GeForce GTX 560 Ti graphics card NVIDIA specifies a minimum of a 500 Watt or greater power supply that has a combined +12 Volt continuous current rating of 30 Amps or greater and that has at least two 6-pin PCI Express supplementary power connectors.
The Corsair Builder Series CX500 V2 (CMPSU-500CXV2), with its +12 Volt continuous current rating of 34 Amps and with its two (6+2)-pin PCI Express supplementary power connectors, meets the minimum power supply requirements.
The OCZ ZS Series 550W (OCZ-ZS550W), with its +12 Volt continuous current rating of 38 Amps and with its one 6-pin and one (6+2)-pin PCI Express supplementary power connectors, is sufficient and gives you a little more spare capacity in reserve than the Corsair CX500 V2.