If I were you, I would just not overclock. I have a 5500 and as soon as I got it, I was like doh I could get more so I played with overclocking and fried my video card 6 months later. No big deal, got another one but be sure that now I do not overclock anymore! what you gonna get? 5 more frames per sec on your favorite FPS for a computer that you paid $3,500+? Then you fry your stuff, if you're lucky, only the video card is damaged... And the worst is that you have to wait for ever for AW to send you the new card. I do not think it's worth it. Overclocking's got only sense if you bought cheap stuff (like a proc at 150 bucks) that can be easily overclocked and if you fry it then the final cost is minimal - now if what you bought is 4000 dollars, overclocking it has no sense at all. Just my 2 cents...
