I know this has been solved already but I'm just going to re-assure (and help other forum members overlooking this thread)
I have an i5 2500k at 4.4GHz (1.3v) and a 560 Ti (also overclocked), so the power consumption should be pretty similar to your build. with my watt-meter at the wall I measure my PC using 440W with prime95 and furmark running. add the rough 80% efficiency into it (I have a GS700, an overkill) and you get 350W being drawn from the power supply, so 600 is plenty!
You might have enough for a second, but not enough for a second and OCing head room. Your PSU has 576W, and a 77W CPU with two 220W GPU with 50W for board and drives is 567W. No where near enough to allow OCing on the CPU or GPUs. It is in fact so close to what the GS600 can do that I'd suggest getting something stronger if you want to SLI the GTX570. (or might want to later on.) You are fine with one, even with OCing. But not really fine to two.