i hv a extra gtx 460 in my room now.
Should i turn it to a dedicated physx card? ( or sell it )
how much performance will it improve? (gtx 670 sli going to run 3D )
is it really worth it??
Will it reduce the PCIe channel ??
Odds are (and I can't seem to find the article at the moment...) if you were to add that card, you might experience lower performance. In layman's terms, it just can't keep up. There really only is one way to find out though. Plop it in there, and giver a shot. Let us know the results
Not worth it at all, sell it. The GTX 670 sli you said you will use will be overkill for Phsyx so need to have an old space heater in there as well. You can always test it out but I seriously doubt it would even help 1 FPS.
A dedicated PhysX card will only be used in games that use GPU accelerated PhysX, so it won't help in many situations. You might not even have a game that supports it, so testing it in some random game will likely result in no improvement.