@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 :-)
That is ridiculous to watercool all of your cards, with that money you could build several more rigs. Hell, it'd probably be cheaper to buy a window AC unit and blow that sucker at the systems. Though I will say watercooling would be a great way to have all of your heat exhaust outside of your house if you have any rigs in your house.
Anyways, the notion around this forum that overclocking will destroy your cards is also ridiculous, do some research, visit some forums and find out how it's done. There are correct ways and incorrect ways to approach overclocking your cards. There are also things that should be done to your cards. Reseat the heatsinks with better TIM, space them properly and have good airflow.