I was wondering if anyone knows if adding a PhysX card to a GeForce 8800 GTS SLI setup would make a difference in quality and or framerates. There is a lot of conflicting info out there about the benifits of a PhysX card with PCIe cards. Anyone know for sure?

Generally, it's not worth it.

First, I think it's much cheaper to buy two 8800GTX in SLI rather than two 8800GTS then a Phsyx card. I think.... =P

Second, not all games support the card.

Third, since NVidia announced that they're planning to integrate Physx on NVidia cards, probably the card will be obsolete.

Only a select few games support it.....if a game does not support it, the card will do nothing for it....

A list of games running PhysX, both software(like console games) and hardware(the few that do...City of heroes does have a decent gain physx as does some mods for unreal 3)....
http://www.ageia.com/physx/titles.html

From what I've read on the web..

Nvidia bought Ageia, and now their trying to port the PhysX engine into their CUDA driver which is supported on the Nvidia GeForce 8 cards. When it's done then it will be provided as a free driver update.

PhysX cards are like the fingerprint readers of laptops, they only sound nice when it comes with the bundle, but pretty much useless with most people. If you do have money to waste, then a PhysX card is one thing to waste on, though a Fatal1ty Sound Card would be a better thing to waste money on (though it's still a waste).

And yeah, there aren't a lot of games that support them anyway.