I tried underclocking my 6950 with MSI Afterburner, but it seems the memory will not underclock at all. At 1v and 700/1250 mhz the card is mostly stable but sometimes rarely it hangs up. I'm running it at those speeds with 1.025v, seems stable so far. Load temps dropped a good 10c (using a scythe cooler + noctua fan).

At 0.975v the card ran fine for about a day before locking up. At 0.950v it locked up outright when I launched a game.

I'm aiming to reduce my power bill as much as possible, without having to part with this awesome card and without giving up too much of its performance.