
Should be even cheaper than that. An Athlon 1.4ghz is enough to really get a big benefit from a faster card than you've been using. As for nVidia cards being better for gaming that is a bit of an over-simplification.

GF4MX are slightly enhanced GF2 technology and significantly slower and less capable than a GF3. GF3 come in TI200, std and TI500 forms in order of speed but these cards do lack in non-gaming areas. Hence the GF4TI line, enhanced GF3 which are not only faster but address the GF3's non-gaming short-comings too. All Radeons are very good at the non-gaming aspects so lets have a quick look at what they're equivilent to. The Rad7500 is on par with a GF4MX440 so in terms of speed you're about GF2TI. The Rad9000 is the same speed but now you at least get DX8 hw which the GF2, GF4MX and Rad7500 don't have. The Rad9000PRO is significantly faster and near GF3 when it comes to gaming, the Rad9000 series is a cut-down cheaper to make Rad8500 so the 8500 is actually better. The Rad8500 series is easily as good as the GF3 in gaming areas but as mentioned the Rads are VERY good in non-gaming aspects too. The Rad9500 in terms of pure 3D speed is just below a GF4TI4200 but you now get DX9 hw (GF4TI are still DX8), not that it's useful at the mo or for the next 12 months but it's there non-the-less. The Rad9500PRO is easily on par with a GF4TI4400 while the Rad9700 series are clearly faster. The Rad9500 to 9700PRO are all fantastic at adding full AA & AF but to really get a sizable gain over GF4TI you need a very fast CPU, at least XP2400+ / P4 2.4ghz ideally.

So essentially a Rad8500 esp with 128MB or GF4TI4200 (std 64MB ones have faster RAM than std 128MB so either are very good) are VERY fine choices, anything above these and you really want to be looking at Rad9500 cards pref in PRO form. One thing to look out for is clock speeds and if you're in to o/c'ing the type of RAM (as in ns rating) used, this is esp important for Rad8500 cards where the speeds can vary VERY significantly. If you get a GF4TI4200 the brands to avoid are Evga, Aopen and Gainwards esp the non-GS ones, other than that brand makes VERY little diff for GF4TI cards.