you forgot to psot your price tag for the gpu. right now the 7750/7700 are the best low cost gaming cards. new egg this weekend having sales on the 650ti cards. you get better fps for the dollar with ati cards.
look online at some of the youtube videoes of sites that test the 7850 vs nvidia cards. http://www.eurogamer.net/videos/battlefield-3-1080p-dx1...
the game clip does drop a few f bombs. what you want look at is frame rate of 650ti in most games to the 7850. then try and get the most bang from your $$$.
1 more ques. does nvidia's physX really make a any difference to gameplay physics along with all those other nvidia specific features(purevideo etc.) or all gpus handle physics in similar manner ??
physx support is specific to nvidia cards only. amd cards don't play well with physx enabled as physx's load is shifted to the cpu. you may use an nvidia card as a seperate physx card if your motherboard has an extra pcie slot (x16/x8/x4), then you gotta pay extra for the card.
physx's usefulness is subjective. some people like it, some don't care, some dislike it. it's up to you. try watching some gaming videos with physx enabled and disabled. better, try playing physx supported games in someone else's pc with physx enabled/disabled.