To push it further, you need to give it more power; turn up the voltage. Only touch the voltage if you know what you're doing. If you're new to overclocking, I recommend you do some research, and experiment on a less-expensive card. Your fanspeed should be based on a curve ideally, not a set value. If your temps are below 90C, you're safe.. but I wouldn't recommend running at that temp 24/7. I would shoot for 75C max as a safe 24/7 temp.
Only the 2GB cards can be flashed to a 6970 BIOS. That's why most people don't buy the slightly cheaper 1GB version. I'm actually using a 6950 BIOS that was patched to unlock the unused shaders... I'm not sure if the 1GB 6950 can use that one, but it's worth a look.
I tried power control at 20 and changing to 875Mhz, but the ATI's software began throwing up errors that the card had stopped responding to commands. I'll just have to leave it at 850.
Thanks for clearing up the 1Gb/2Gb 6950 card issue. I was wondering why reflashing wasn't working even though I was following the instructions. 330Mhash/s isn't too bad for a budget card anyway. I'll get something better next time.