Aah, decisions decisions. I'd just sold myself on the Sapphire 7970 OC, until I saw how similar the 7950 is when overclocked.
Alas, I think AMD have won this one - 7950 it is.
As much as I would love to side with the nVidia team, the price and performance of the 7950 is just too strong. Especially with the Sapphire cooler, which is near silent. If I play a game with lots of Physics I shall just have to rely on an Ivy Bridge CPU clocked at around 4.7 GHz - if that's not sufficient then I don't know what is
Thankyou all.