433 isn't that hard for a 6800GT. I have had mine up to 450/1150 before on stock air. The only things done to the card was a BIOS flash to a Golden Sample GT BIOS and 1.4v performance 3D, the stock cooling was lapped and AS5 was applied to the RAM and Core, and I'm using Riva Tuner with the OC Test disabled. The OC Test lies to you. You have to test for stability yourself. The OC test will always give you low OC's.
On Drivers, some 6800GT's hate the 8x.xx drivers. On mine the system was an unstable beast that would crash back to desktop and 16 colors, would BSOD with a nv4disp.dll error, and I even had a few random reboots flying LOMAC which a Combat Flight Similator that works a system very very hard.
My system like the 77.77's. The 77.77's are WHQL approved so should be 3DMark legal.
Every system is different. The best drivers to use are the ones that work the best. You can't say that one driver is best for everyone's system. The only real way to tell is to test different drivers until you find a stable one that gives you the highest scores while still giving good game play and FPS's.