I don't know what kind of computer you use, but I'm assuming you have a similar setup to my Dell Dimension E521 which came with a nVidia (6200, I believe, not sure) and only provides a single PCI slot for additional video cards. I run XP on 32-bit setting, with the same resolution and other settings you do. I immediately knew that I wanted a driver that gave me optimal video performance and have installed the best single-slot PCI card and driver available for my unit, so I installed an ATI Radeon x1650 PRO, which runs on 512 MB DDR2 memory (most single-slot offerings seem to run on 264 MB that I found compatible with my machine). Most of the other 512MB cards I checked out needed two PCI slots with a vent on the upper slot, a slot which does not exist on my processor.
My suggestion is to check with your computer manufacturer on card compatibility and go with the best 512 MB PCI video card and newest driver for the card that is available for your particular processor. If you do decide to get something similar to mine, my only other suggestion is to keep the processor cool and well ventilated to prolong the card's life.
Here is a link to the card I have installed:
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http://ati.amd.com/products/RadeonX1650/radeonX1650pro/index.html