In case anyone was interested, I recently performed a whole battery of benchmarks with and without the 8800 GT as a dedicated PhysX card. I used Metro 2033, Batman Arkham City, and the MARS PhysX benchmark. Overall, there was no significant improvement using the 8800 GT as a dedicated PhysX card.
I had reported before that I saw a significant improvement in testing with Batman Arkham City, but now I recall that was Arkham Asylum not Arkham City and it was with a different machine (I had the 560 and 8800 GT with an Intel C2D E6750 processor), so my apologies for the misinformation. The testing I just performed was also a lot more thorough and repeated several times.
For those interested in some numbers, here are some of my results (all resolutions are 1920x1080):
Batman Arkham City (all settings max including PhysX, Min-Max-Avg FPS):
GTX 560 + 8800 GT: 19-83-49
GTX 560: 29-78-52
MARS Physx Benchmark (MSAAx2, everything else max, Min-Avg FPS):
GTX 560 + 8800 GT: 12.64-20.44
GTX 560: 13.38-22.47
Metro 2033 (MSAAx4, AFx4, DirectX 11, Advanced Physx and Tesselation ON, DOB OFF, Avg-Max-Min FPS):
GTX 560 + 8800 GT: 26.67-67.12-5.20
GTX 560: 26.00-58.14-5.47
Hopefully that helps anyone else out with a similar situation.
post edited by Salahuddin - 2014/12/20 15:22:52