Hello
I have two GTX 570 graphics card reference models (Gigabyte and EVGA). Value of increasing voltage, from experience I can tell you that as long as you do not remove the OCP and the value does not exceed 1.1V voltage, there is no problem with the video card's VRM. Can I say I'm the happy owner of a copy of Gigabyte GTX570 excellent, running it with standard cooling at 1000MHz GPU and 2250Mhz memory, with a supply voltage of 1.1V GPU.
@StrelokL94 you could increase the GPU voltage feeders with 1-2 units and I think you can get things done.