Before upping the voltage, simply overclock the core and memory bit by bit, until the card is no longer stable. Then you can try upping the voltage to get it stable again... Starting with increasing the voltage does no good but increase power consumption... I'm not yet at the stage of increasing voltages, as I've just started overclocking a bit using Sapphire's TRIXX... By the way, I thought the Asus BIOS was that of the factory OC 6950? Doesn't that BIOS have a speed of 810/1250?