the latest driver is 12.7, and for the Xfired 6870's, it was amazing. It dropped temps for me, and increased power in some situations.
How are you installing/uninstalling drivers? Driver sweeper in safemode? If it's been awhile, I would recommend backing up and doing a fresh install of windows, and of all your newest drivers. (12.7)
What program are you using to control the 6870's? Afterburner? I believe 2.22 just came out also.