@Clavulanic: I am running these stock with fan cooling only. I am expanding watercooling to all soon (the watercooled machine is 400MH/s per GPU and running around 60'C). Stock (which mine are, except for 2x cards) are expected to be at 300Mh/s, so I do not understand why I should be way above 7.5GH/s.
If you have any suggestions on how to "fine tune" my operation - let me know. It is always easier to tell someone else to destroy their $800 card instead of your own :-)
Where to begin... first Linux, I'd install it, phoenix, and use 2.4 SDK and phatz kernel. I'd experiment with underclocking the memory on the card, you should be able to find a sweet spot, and at the same time reduce heat production (you don't need the memory speed for mining, by reducing it, you don't hurt anything on the card).
I would expect you should be able to get 8.4+ Gh/s without having to overclock the core.
Phatk and memory underclocking does 0 or negative differance on the 69xx gpus. do read up some before spitting out that.