Also, I wouldn't suggest any card specifically for Physx use. Although I do like Physx in games that use it well (Batman: AA, Mirror's Edge, etc.), paying extra money and using up a PCIe slot in my computer isn't worth it to me. If you want to use Physx in games, buy a decent nVidia card that is capable of running it smoothly. And I can't recommend a good graphics card without knowing the rest of your computer, including your monitor and its resolution, and your power supply.
there arent any dedicated physics cards now, they just use nvidia GPU's for that purpose. Very few games support it so far. If you just want a cheaper one that will work well, a Geforce GT240 will do for a dedicated physx card.