Registered just for this thread. I picked up a Sapphire 7850 regular version for my IB build. I've been overclocking and benchmarking for the past few days, and have found that I've got quite a good card.
All OCs were run from the Asus GPU Tweak utility, and CCC is not installed. GPU fan was set to 40% (which is just barely audible over case fans). All the tests below passed Heaven no problem with no glitching, etc. I also tested in SW:TOR and Skyrim for several hours at the top clocks for stability testing.
I additionally measured power-pull using a Kill-a-watt during the tests. Power pull was for the computer only - no monitor or accessories. Max power was the highest I saw the Kill-a-watt spike to during the test, and the average is from the minimums, maxes, and a bunch of samples in the middle of the run. I additionally have NOT adjusted the max TDP for the card - so it should be still at stock power TDP. I did NOT lock my CPU speed or disable turbo mode for the tests, so CPU scaling may be responsible for some of the power usage increases. However, I didn't see much difference for CPU usage during Heaven benchmarks run-to-run so I think the GPU OCs are responsible for the majority of the power deltas.
Heaven scores are the recommended settings in this thread at my monitor's resolution max - 1680x1050 4XAA fullscreen with normal tesselation.
So yeah, killer clocks for low low voltages. I am wondering if I'm hitting a power threshold since I have not bumped up max TDP for the card; OC 7 at 1200 GPU clock 5600 mem clock gave weird results.
Obligatory screenshot after max clock test:
Even though I'm at such a low clock I'm not going to push it any farther and am probably going to go 24/7 at OC 3 settings - 1150x5400 @ 1.095. I'm maxing everything I play right now with these settings and I want this card to last for quite some time.
Thanks all for all the information and useful guides!