Before mining, would any of you guys have bought mis-matched video cards and installed them in your computers?
folding @ home, contribute to research for cures to various diseases. best on nvidia hardware (as well as CPU clients). all GPUs run independently, same miners, so mix away.
nvidias physx, gives more physics based eye candy for some games. you add a second, usually less powerful nvidia card (or sometimes 1st nvidia card with an ATI primary, but phsyx doesnt officially play nice with ATI cards) to your rig to let the 1st do rendering only instead of both rendering and physx.