I don't think it will benefit you simple because the 2 8800gtx should run the physx faster then the dedicated card. I have 2 gtx260 in sli and when i add a 3rd dedicated physx card (9600gso) my frames dropped a bit in physx. The 2 gtx260 were able to handle the games fine, without a dedicate card. Im pretty sure the 9600gso is faster then the ageia card so it could result in more of a lose. As chef7734 suggested try it, couldn't hurt.