Re: GTX 460 vs 465 vs 470?
Whether you keep the card or swap to a nV card, realistically you'll be better with a dedicated card for PhysX. A second hand 8800GT or similar would be fine but either way a PSU upgrade may be in order to run the two cards. Though a dedicated card for PhysX wouldn't chew power like it would used as a graphics card. In game PhysX only tickles my 260.