A *lot* of people have been disappointed at the actual performance of their MX's. Sure, $90 is cheap and better then an ATI expert, but $50 more gets you a ATI Radeon 32mb DDR powerhouse. Consider saving for a couple more months, not years though.
Also consider upgrading or overclocking that CPU, to a higher Celeron, or Duron (even better). With anything powerful today a 366Mhz CPU will be your bottleneck