The GeForce 4 card has more steps of a graphical construction of a 3D enviorment rendered by hardware instead of software. Therefor, in complex 3D enviorments, it's preformance will be a LOT better. And Unreal 2 is such a complex enviorment.

Other graphics cards to look into (in order of preformance, best last):
GeForce 4 Ti 4200
GeForce 4 Ti 4600
Radeon 9500 (Pro)
Radeon 9700 (Pro)
GeForce FX
Radeon 9900 (Pro)