Need help with video card upgrade for AX4SPE MAX

I've got an old system running on an AX4SPE MAX board and would like to upgrade the video card to get a little more life out of it since I'm not ready to build a new computer. The system is running 1GB of Kingston HyperX PC2700 cas2 memory and has a 420W Thermaltake PSU. (I'm willing to upgrade the PSU if necessary along with a newer video card. )

The current video card is an Albatron GForce FX5600P Turbo with 128Mb onboard. I would like to upgrade to at least a 512Mb video card. I've been looking at the

GIGABYTE GV-R465D2-1GI Radeon HD 4650 1GB 128-bit GDDR2 AGP 8X
Newegg dot com item # N82E16814125281
(sorry, new poster, can't post links)

which is a 1GB card, but both Gigabyte and Aopen are telling me that since 1GB cards weren't available back then, they can't say if it will work with the 865PE chipset on the Aopen board...

So, can anyone recommend a good, compatible, and most importantly, stable video card for the AX4SPE MAX...? I'm looking for something in the 512MB range or, if it's certain to be compatible, a 1GB card... I don't want to spend *too* much as it's a 6yr old computer but something in the general $75-150 range would be ok.

Any help would be greatly appreciated, and thanks in advance.

Erin