Wow! Impressive! What voltage are you feeding that monster? I'm running the same chipset on a different board (with lower temps) and I can't push higher than 750mhz with a .06v increase. I could definately push the voltages harder, but I haven't tried.
At 800mhz I have the driver crash running the "Heaven" benchmark.
Increasing from my board's stock 650mhz to 750 (+.060v) gives me a 8.65% increase in FPS, and takes me from 263 to 283 points (I'm running a 640x480 dx10 AF1 AA0 benchmark)
EDIT: Whoops, I forgot AOD manages the NB Voltage as well, and my auto-settings were removed by AOD once I got into windows.
I set AOD to +.060 NB Voltage (1.168v total) and the bios to 800mhz. I finished a low res Unigine Heaven benchmark with a 11.5% increase over the 650mhz "stock" (overclocked) speed! This is great for me!
I've not confirmed this to be stable by any means, it was just stable enough to run a benchmark. I'm going to run a 3dMark06 benchmark, reclock it to 500 (stock, not overclocked) and do that again to get a total overclocking increase.
I highly recommend backing your NB voltage down and using 800mhz with sub-1.2v just for heat reasons. 1.35v, while it may not be terribly dangerous, is going to heat up your NB a ton. If you don't have a fan on that heatsink it can overheat and fry your board.