I agree with everything Cavalier said. Not only should AA be disabled, but make sure AF is too. Try running at 800 x 600 with 16 bit color.
You didn't mention what CPU/Mobo you have, which has a bearing on how far you would go with a better video card, but that's probably the single best thing you can do. The 9200SE needs to go to a non-gaming computer.
You can trade in your 9200se to ATI for a 9600 XT. You pay $169 up front to ATI for the 9600, and when you mail them your 9200 they send you back $50. Total cost $119 plus shipping.
But if you have a Celeron 1.4 Ghz cpu, then there's not a lot you can do until it's time to upgrade the whole shebang.