This would be considered a fairly mild OC'ing. Over-volting your GPU will get you more results, but reduce the lifespan of your card. I have mine running at 1.00v (extremely conservative) and am getting a stable 930MHz core and 2052 (stock for my card) memory speed. My 3Dmark11 score is 4320, and I have a similar rig to yours. I would say, unless you really need more performance, leave it as it is. Over-volting will get you more, but unless you are being fairly aggressive it will only net you another 4-6 frames per second. To me, that's not worth it. I haven't got GPUs to throw away.