Well I'm not sure but you might want to upgrade your card to the GeForce 6000 or 7000 series because usually those cards would give you a higher resolution, but you have to remember most new cards are now AGP 8x or PCI express, so unless your planning to buy a new motherboard to support your new videocard your pretty much out of luck.
If your planning ot go to a cheaper route you might want to consider cards from ATI or Diamond you can check their website and see if they sell any low range cards for your budget.
Today I bought (and absolutely LOVE) a new NEC 20WMGX2 monitor (flat TFT, 20", 16:10 aspect (!), all the bells and whistles. I connected it to my PC which is running XP Pro, Intel P4, 3Ghz, 1GB RAM, with a GeForce FX 5200 PCI video card.
The montior is supposed to be running at 1680 x 1050 @ 60Hz for optimal performance. My card is only giving me 1440 x 900, and tech support said that it came out just before the wide aspect monitors went mainstream, so it won't go there.
I spent plenty on the monitor and don't want to spend much on the card, just enough to do the trick. What's a sweet spot for my needs.... thx!