I have the 8800gts and its a stunning bit of kit, custompc.co.uk reckon the extra money for the 640 over the 320 is worth it (I have the 640).

Last night I had a 22" and the 40" running from it with Team Fortress 2 on the 40" and a film on the 22" and I was getting no problems at all from it. I am not saying the other cards can not perform as well, I just know how good this card is.