You cant run them in SLI, if that is what you are asking.
The 560 could be assigned as a physx only card, but actually the 960 is good enough to handle graphics processing and physx (if you happen to have a game that uses physx) both. Adding a second card and dedicating it for physx was a good option a few generations back when most GPU's were not powerful to handle both functions well at once, thats not really the case anymore.