Hi!
I wouldn't buy any cheap GF2 in your system. Correct me if I'm wrong, but GF2 MX will be a bottleneck.
I have P3 933 and elsa GF2 MX 32MB.
I ran winmark 2000 helicopter test with 1280 16bit and medium detail. With default settings I had something like 35 fps.
I then changed (can't remember what feature it was) graphics acceleration(or something) from GF2 to processor. FPS went over 40! So I guess if in my system GF2MX is bottleneck, it sure will be in your system too.
I should buy another videocard, perhaps GF2 GTS or Kyro II 64MB?