I have a question about running an amd and an nvidia graphics card at the same time

On tuesday or wednesday i should get the last piece to my new pc. Currently im running a gtx 460 se. I will be getting an xfx 7870 ghz edition(i wanted an 7950 but my wife said she felt more comfortable with the price of the 7870). But i was wondering is it worth it if i use the nvidia card just for physix? Or will that just cause more headaches?

If you have a decent CPU, I'm sure it'll run off of that.

It is possible through hacks/mods but I have no clue how.

There is something out there namet HyperSli you can try that :-)

Can you even use both at the same time!?

 

Edit...

This looks intresting, but cant help feel its a tone of fucking around just for PhysX

http://www.ngohq.com/graphic-cards/17706-hybrid-physx-mod-v1-03-v1-05ff.html

You're screwed.

or you can use the trick I use where you get physx to run over cpu insted or something like that it works with my system and I use a AMD gpu here is a link 
http://www.nvidia.com/object/physx-9.12.0613-driver.html

I dont know where i saw it but i thought i could just select to use my gtx460 se as the physix card and use the other card normally.