I use "Asus GPU Tweak", there is an "Overclocking range Enhancement" setting and after enabling that, This utility is letting me go past 1200 MHz (1250 MHz Stable) and it also lets me overclock memory which is now at 1750 MHz stable.
I get 9-15% fps improvement over default clock. approximate average TDP has increased from 65 W to 105 W GPU , because It automatically adjusts core voltage to 1.310. I know its high, 1250 MHz may be achieved with lower voltage. Though I didn't manually try lowering voltage at this core frequency.
And 1400 MHz my foot.
You'll probably need 1.55v and Liquid Helium.
Edited by sumitlian - 5/18/13 at 2:13am