Yeah, to go along with what tortnotes said, even if you got an NVidia card in the same range as a 4650, you would not want to enable any serious PhysX. It is fairly GPU demanding and would cripple a card in that range.
------------------------------Phenom II X4 940 BE 3.0GHz - 1.25V > GA-MA790GP-DS4H > XFX ATI 4850 1GB > 4GB OCZ Platinum 1066MHz 5-5-5-15-2T > PCP&C 610W
Athlon II X2 250 3.0GHz > GA-MA770T-UD3P > Sapphire ATI 4650 512MB DDR3 > 4GB OCZ Platinum 1600MHz@1066MHz > XP/Win7 Enter 64
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