PhysX?
I don't know.
You may want to post this question in the Technical Issue forum under Development. There are a lot of smart technical people who read those and help us technically deficient people.
City does not recognize PhysX unless it is the standalone card. This is a drawback of the game, not the PhysX on your video card. City would need to update its engine (or whatever) and various other background junk to utilize the GPU PhysX in addition to the standalone card.
Paragon Wiki: http://www.paragonwiki.com
City Info Terminal: http://cit.cohtitan.com
Mids Hero Designer: http://www.cohplanner.com
Basically, the game uses it's own built in version of the PhysX library. This version is OLD and doesn't support the new nvidia cards. It's not user replacable...so as far as I know, you're out of luck.
I was wondering why I cannot enable PhysX in the game when I have an Nvidia GPU with physX.
It is enabled in my drivers, but the option is greyed out in the game. =(