PhysX or not PhysX ???, ... it's needed or not?

A member asked me if PhiysX card is or not necessary to the great XPS performance with two SLI GTX 8800 video cards
I really not sure if it's a must or not, but I found this link :

http://www.hexus.tv/show/2007/10/PhysX_As_..._DELL_XPS_1730/

There's a video explaining some reasons to have PhysX inside your XPS.

But, more better, I found this other video showing differences between a PhysX VS NO-PhysX game.




Your Pet

....and, just to finish, this video to give an answer to the member, that explain why PhysX is needed to dual SLI 8800 gtx owners too.




your Pet again

thank you!

Physx is really great when the game is optimizing for this. Without this, I don't think that there's a real difference.