I had nothing to do so I decided to build something...
Core 2 Duo 8400 3GHz
GTX 780 Dedicated PhysX card
(Yes I know doing this is dumb, but I like doing random and useless stuff for fun)
I haven't done any benchmarks yet cause the new drivers decided to delete the older ones and right now I'm too lazy to download them again
But I did some testing with a Quadro FX570 this morning (With 8400GS as main card) and it ran borderlands 2 on the lowest settings at an average of 21FPS with PhysX off and 23FPS with PhysX on