here are the actual specs broken down for the GeForce2 Ultra, so you can see how close a particular card comes to the nominal minimum to run AH2:
GeForce2 Ultra Specifications
GeForce2 GTS GeForce2 Pro GeForce2 Ultra
Process Technology .18 micron .18 micron .18 micron
Core/Mem Spd 200MHz/333MHz 200MHz/400MHz 250MHz/460MHz
Memory Amount 32/64MB 64MB 64MB
Memory Bandwidth 5.3GB/Sec 6.4GB/Sec 7.4GB/Sec
Pixels/Clock 4 4 4
Pixels/Second 800 Million 800 Million 1000 Million
Texels/Clock 8 8 8
Texels/Second 1600 Million 1600 Million 2000 Million
Polygons/Second 25 Million 25 Million 31 Million
