
 The GF4TI cards scale a heck of a lot better than Rad8500 and GF3, in that they take far more advantage of the faster CPUs (great when deciding to upgrade). If you are down around 1ghz then there is only a small diff between GF3, GF4TI and Rad8500, but when you get to 1.4ghz+ the cards really begin to spread out.

 As a rough guide, your Athlon1.4@1.5ghz in 3Dmark2001 (card: total, games1-4 hiQ FPS):
1024x768x32:
Rad8500: 9300, 50, 85, 62, 53
GF3TI500: 8600, 50, 72, 60, 53
GF4TI4200: 11000, 54, 112, 69, 60
1024x768x32xAA:
Rad8500: 5000, 37, 45, 38, 21
GF3TI500: 5500, 37, 47, 43, 27
GF4TI4200: 7000, 38, 72, 47, 31

 Of course different games show different distinctions between the cards. In any case, there is no doubting how pointless the GF3TI500 really is now, for the same price (or less) the Rad8500 is better, faster, image quality, TVout, dual monitor etc. The Rad9000 is a worse buy than the Rad8500, so that leaves the GF4TI4200 which is more expensive but doesn't really have a weak point. O/c'ed you should expect to get within 10% of the GF4TI4600 and the AA perf along with 3D perf, image quality, dual monitor etc are very good too. Unfortunately ATI have done Rad8500 buyers no favours by releasing the inferior Rad9000 card, whereas nVidia are not using GF5 for their new card, which all helps give the 4200-128MB a longer life and makes it easier to sell on later.

 If you have < $100 then ATI Rad8500 (& LE) are great cards, if you can fork out the extra cash, and want the top all-round perf (esp AA) but without breaking the bank the 4200 is a great buy too. Whatever you get, go for a 128MB version, and if you go Radeon either get a true ATI (and pref retail) or else a large discount 
