Second GPU for Phyx

I am planning to purchase a new GTX770 GPU and use it as my primary GPU. I have an old GT 240 GPU.

I want to know if I use 770 in x16 slot and 240 in x16(running at x4).

so will this configuration work or not.

I believe any nVidia card that is a 8800 or above with 256MB of RAM can be used in SLi as a PhsyX Card though I am not sure if it will have much effect since the 770 is rather powerful it might be less Hardware support.

GT260 has 192Cuda Cores while your 770 has 1536. You could always try, it does support it though not sure if you will notice much of a performance boost.