I have the evga gts 320mb superclocked, and I have it overclocked to 680/980 easily... doesn't even get too hot (regulating fan with rivatuner) It's a very nice card and I have been very happy with it. 
11223 on 3DMark 6 after overclocking it and my Intel e4300 Here's my 3dMark Link

11223 on 3DMark 6 after overclocking it and my Intel e4300 Here's my 3dMark Link