Here is another site where you can compare vid cards :
http://www.gpureview.com/show_cards....=628&card2=641
I have a ATI ASUS 6870 that I am very happy with. I never had an ATI card before, I was strictly Nvidia. I upgraded a month ago. Vid card was my last and toughest decision and I finally got the 6870 for a good price at Tigerdirect.
http://www.tigerdirect.com/applicati...351&CatId=2306
Go to the first link I gave you and put in the 6870, it compares rather well with both the Nvidia cards you listed and its $244 at Tigerdirect. It also uses less power than either the Nvidia cards which means it should run cooler.
Not trying to change you mind, just giving you some food for thought.