I think that might just be a problem with your card? With the unlocked bios my fans went a lot louder at 100%, so it worked fine. I set a profile with the fan speed 10% higher than the temperature (eg 70% speed at 60 degrees), and that keeps it below 70 degrees, but it gets noisy at over 70% fan speed.

The voltage and clock droops at 70 degrees are a terrible thing, thankfully my Vram keeps running at silly speeds. I decided to increase my 24/7 Vram clock to 7400 Mhz, and the maximum stable without artifacts is 7529 MHz ... More than enough to compensate for my lousy GPU clocks.

But then the awesome Galaxy / KFA2 GTX 680 white PCB does 1300 / 7800 clocks, and now I wish I had one of those instead.