PhysX (when it was made by Aegia) used to be a seperate card instead of being integrated onto the graphics card, then Nvidia bought them out to capitalise. Every Nvidia I have had has crapped out on me, and yet I have had no problems with ATI (using an HD4850 at the moment), so they can shove their physics hardware acceleration up their arse - it really doesn't make much of a difference to me, and I have seen the comparison videos.