''Physics card'' ? You sure? Nvidia and ATI are supposed to be using havoc FX and the same video cards that they sell .
Ideally , instead of needing two video cards , or a video card and a physics board , one fast card could do all your work eg. 8800GTX , since all 128 of the processing units are identical , you can dedicate 16 for your physics and still have plenty for graphics.
Maybe if we lucky they would allow boards with integrated graphics be used as physics processors , i hate the idea of having to buy another card to play games.