I have been trying to overclock my 2 gtx 560 fermis and I have had them at 900mhz no problem for about a year now. I have a aftermarket cooler on one of them and the other ones just stock. at 900 mhz on Heaven they maxed out at 70c. I want to go to 950 mhz but I tried it one time and after a while it froze on me. Am I as high as I can get?