Renember the nvida suppot physx directly (hardware physics like cloth,fluid...)
and check what tecnology for every card (45 nm, less hot and power consumation)

correct, but at this point amd cards were faster than those from nvidia. that's seldom but true... not any more, but the hd series was also cheaper. so: good choice.

can anyone tell me how to actually install/use physX with 3dgs?

sorry I've never used a 3rd party tool.

someone would need to write a plugin if they want to use phys x in 3dgs. I would go with the nvidia card as ati cards sometimes tend to have problems rendering shaders

It totally depends on the shaders themselves though. Don't take it the wrong way, but the brand doesn't define how well a shader will run. Nvidia cards tend to be quicker but less accurate and detailed. Of course, this too is just another equally silly generalization,

Cheers

what about newton is that a physics engine i could use with 3dgs?

if so how do I get it to work.

sry I'm a noob