Will a 9500gt can be added to gtx560ti as a sli config


Install the 9500 GT in another PCIe 16x slot. Then go to '3d Settings' in Nvidia Control Panel. There you can indicate which card you'd like to dedicate to PhysX processing. Choose the 9500GT.
 
^Maybe, though I think the whole idea of using a dedicated PhysX card is to take the PhysX load (which is only a fraction of the GPU load) off the 560 ti will allow the 560 ti to operate at an optimum level. I don't think a 9500GT would choke the system processing the PhysX data.