quandao93 :
Spectre694 :
It will slow it down. For Physx you need a card in either the same generation or at most one behind (high end) otherwise the other card cannot keep up with the main cards causing them to wait on the physx to finish
can you recommend me the best physx card for my set up?
Based on past experience I would say 670 decent or 680/760 better. Honestly though I don't think you will see much of an increase in FPS those 770 should tear through PhysX by themselves just fine.
If you have multi-monitor setup 3-Way SLI would serve you better than a PhysX card. Any particular reason you want a dedicated PhysX card?