A Physix card, heck yeah!
OMG, I just tried this out, what a fantastic treat! OMG, OMG, OMG! I put an old GTX9800+ in my board, along with my GTX670SC, went into the Nvidia controls, told it to use the 9800 as a Physix card, and holy carp! OMG!
Holy carp!
(yeah, I know this was said before, but the search function on this board doesn't work) Wow, what a difference! Dang!

Holy carp!
(yeah, I know this was said before, but the search function on this board doesn't work) Wow, what a difference! Dang!

The reason I asked is that I am about to start planning/shopping for a homebuilt rig. I've only built a couple of hundred so hopefully I can figure it out. 