I wonder how expensive it'd be to have an extra nvidia card just for physx, it shouldn't need that much performance, especially if the actual graphics stuff isn't running on the same card
@noiob almost nothing supports it and so few games have physx that if you have a 9 series card or newer you'll likely be able to run the game+all the physx you could want
then again not that many games use physx extensively to begin with, I know about Borderlands 2 and Mirror's Edge (though ME really shines with it)