I was just wondering if you have an ATI Card as a Primary could you use an older Nvidia Card just to render Physx. Might be a way to have my cake and eat it too but I seriously doubt you could do that.
I've done it so you can but just need an empty PCI-e port. Can't mix Radeon with nvidia though so you will have to get the PCI PhysX card which is probably obsolete by now in terms of GPU and memory clock. I don't think all 8 series or higher will work but lookup CUDA enabled nvidia cards and you can find a definitive list.