Hi, I just bought a new PC and am in the process of putting it together.
My processor is an i7-2600k and I'd like to overclock it - not massively, as this will be my first time, but somewhat, probably to whatever the standard is before I start having to fiddle with voltages.
Right now I have a single 560ti in my rig and in the future (a few months) I'd like to get another and SLI them.
A good 700w PSU would definitely be able to power a build with two GTX 560 Tis. However with the ModXStream Pro 700W you have to worry about the number of connectors you have, as it only has two PCIe connectors.
You could use molex to PCIe adapters, but you would have no molex connectors left for anything else such as fans. So as long as you don't need any molex connectors for anything else then you should be okay.