im confused of choosing gtx 560ti and ati 6950 ...im going to nvidia because if physx i want to play games at high settings with physx turned on at 1920x1080 res without lag..will gtx 560ti will perform better at high res with physx turned on
You are making a big deal about wanting PhysX to improve performance, but I want to make sure you realize what PhysX is, or have a use for it. PhysX is not a performance booster that helps all games. There are 20ish games that offer GPU accelerated PhysX. Only these games show improvements with a PhysX capable card. All other games will not use the graphics card for anything other than what every other card does.
What physX games are you trying to maximize performance with?
Edit: seems you wrote your post after I started mine. So Mafia 2 is what you are building this system around? Now let's take a look at some benchmarks for Mafia 2.