Thank you for your input. But suppose I add two more monitors. Would the third card be worth it? Also, would it be competitively similar or even possible to use the 9600's in sli and the 260 gtx as dedicated physx card?
9600 GT sli is slower than 260 GTX so that would be a waste. If you want to add 2 more monitors then you would need to un-sli the 9600 GT with the result:
260 GTX for gaming, 1 9600 for physics, 1 9600 to power the other 2 monitors.