I just overclocked mine to 240/550 tonight. When I tried 250/550 it did some really wierd things with a nice light show on the screen. After turning the machine off, rebooting, and readjusting the card back to 240/550 everything was fine. You might have better results than me but as you get this high I think you start to see diminisheng returns with every new setting. Play with it if you want but the card is damn fast at 240/550.