I have 2 running both at around 705. One is a Gigabyte and the other is a Sapphire Dual-X. They both have to be tuned differently. One runs at 80 C and the other at 68C. Oddly enough with auto-fan, one needs a targe temp at 68C to keep the GPU at near 100% load while the other needs a target temp at 82C to keep a load of 100% GPU. It took me a while to figure that one out!.

Running at 340 clock speed and 1200 GPU speed on both.