For a system using two GeForce GTX 560 Ti graphics cards in 2-way SLI mode NVIDIA specifies a minimum of a 700 Watt or greater power supply that has a combined +12 Volt continuous current rating of 50 Amps or greater and that has at least four 6-pin PCI Express supplementary power connectors.
Your Corsair Enthusiast Series TX750 V2 (CMPSU-750TXV2), with its +12 Volt continuous current rating of 62 Amps and four (6+2)-pin PCI Express supplementary power connectors, is more than sufficient to handle the addition of a second GeForce GTX 560 Ti and do some overclocking.
Thanks for the info. I was looking for nvidia's minimum spec for SLI and couldn't find it. Could you direct me to where you found the 700W/50 amp minimum requirement?