If you dont know what Physx is, or havnt heard of it before, then you seriously dont need it.
Ive known what physx is and have been following it for years, and I still dont need it, nor would I spend money on an Nvidia card just for it. I were tempted a few times, but at the most it only seems worth around £40 to me, and you cant get a card for that much that would be capable enough of using as a Physx card.
Most people who choose to combine ATI cards with Nvidia ones for Physx usually only do so because they have an old Nvidia card lying around that can handle it, or they buy a second hand one for cheap.
Firstly, Physx with an Nvidia card running alongside an ATI one is not officially supported by Nvidia, they require old, modified, or 'bugged' beta drivers as Nvidia refer to them as.
Secondly, the number of games that you would get any benefit from using Physx is minuscule, and the difference really isnt worth getting so hyped up over or spending around £60-80 for a capable brand new card to handle Physx.
You will get way better results from just adding a second 5770, if you currently only have one than you would from buying an Nvidia card for Physx.
If youre still interested, then the minimum card reccomended for Physx use is a 9600 GT. The best and most ideal card from a price to performance ratio would have been the 96 shader 9600 GSO, as the speed of the card is pretty much irrelevant, what helps is having more shaders. But anything higher than a GTX 250 would be a complete waste.
Id only go for it if you can find a 64-96 shader Nvidia card for <£40.
