Physics X or CF

i've 5670 512 mb and h55 mobo with 16 x + 4 x

what should i do

- purchase another 5670 and do CF
- or purchase nvidia card which is cheaper than 5670 for physicsX (i think nivida + ati is not possible but i've recently read a recepic for this from tom's hardware recently)
- or wait and save for stronger card.


third option is the best but i want to save the money as much as possible and i don't game so much (max 5-7 hours a week).

so plz give me ur opinions ( ***** i want to know which one is better for gaming in first two options as my knowledge)

thanks u all