overclocking sucks on the Diamond 6970. Temps are great (never hit above 78 celcius), but voltage to clock ratio in terms of overclocking is just bad.
I got mine to 930 / 1400 at 1.2v
At stock voltage I can't go past 910 / 1400 (1.175v)
In order to get 960 / 1450 stable, I have to go all the way up to 1.40v. And at 1.25v I'm not even stable with 940 / 1400. >_<;
Sorta wishing I went with the 570. Though idk maybe I'd hit problems with that too. Whole reason I got the 6970 was because the GTX 460 I bought was broken out of the box (plus my previous 5770 was a great card at stock). The 6970 is nice at stock, just wish this enthusiast card would act like one and allow some overclocking.
if you're using eyefinity and/or maxing out settings on your games the 6970 eeks past the 570 at stock speeds. i'm not familiar w/ 570 benches OC'd though, so maybe it's better once you bump it up?