basically the choice of physx required nvidia setup mean nvidia cards should be good from radeon in physx mode however it is simple get something like gtx 460 as a normal card and get the card lik 9800gt or any model which support physx features put the physx card in the other pci e lane whether it's 4x,8x or 16x.
NVIDIA ® PhysX® is a powerful physics engine enabling real-time physics in leading edge PC games.
PhysX software is widely adopted by over 150 games
and is used by more than 10,000 developers. PhysX is
optimized for hardware acceleration by massively
parallel processors. GeForce GPUs with PhysX provide
an exponential increase in physics processing power taking gaming physics to the next level. What is physics for gaming and why is it
important? Physics is the next big thing in gaming. It's all about
how objects in your game move, interact, and react to
the environment around them. Without physics in
many of today's games, objects just don't seem to act
the way you'd want or expect them to in real life.
Currently, most of the action is limited to pre-scripted or ‘canned' animations triggered by in-game events
like a gunshot striking a wall. Even the most powerful
weapons can leave little more than a smudge on the
thinnest of walls; and every opponent you take out,
falls in the same pre-determined fashion. Players are
left with a game that looks fine, but is missing the sense of realism necessary to make the experience
if your using an AMD card, you need to get an nvidia card with hacked drivers, its the only way. Some games allow you to put the physics workload on your CPU, like MAFIA II, but it dramatically kills your FPS.
is it worth it ? I only have one pci 16 slot anyway
some Physics processing can be done by your cpu if you use a radeon card with no physx.
However, there is a PCI card available that is a dedicated Physics Processing Unit (or a PPU). These can be put into one of the old style PCI slots. There is also a PPU for pci-e x1 slot, though I cant find any uk sellers. The PCI version of the card is available here: