Old AGP Card for WoW

My brothers ATI 9800 AGP card busted today, started artifacting like crazy. My bro mostly plays WoW, War3 and similarly demanding games, but nothing too big. So we went over to Staples and bought an FX 5500 as a quick replacement, but it seems to be insufficient (it was pretty cheap, so it was worth a try, atleast). He's getting frequently under 10 FPS in battlegrounds, when the 9800 was getting 50+. And this is with the graphics specs/res turned down.

Anyways, after he installed the CD drivers I told him to get nvidias latest drivers, they didn't do much. First question: Does anyone happen to know what are the best nvidia drivers for this card? I think an FX5500 should be able to run WoW. Keeping this card would be best case scenario, so if anyone can make some recommendations on this it would be great.

Next, we can take it back to the store within 30 days, but he will need to get something better (we can get something online in that time if needed). He only has a 250W PSU though, so he might need to get a new one of those.

So what is our best course of action here? He only wants to play WoW, and he certainly doesn't want to spend much more than 100 bucks (don't even recommend getting a PCI-E motherboard - it ain't happening). Assuming we get a different card what should he get, and what PSU should he get? Plus, how much power on the PSU, and what cost should it be?

Thanks.

P.S. I don't think he can overclock - it's a Dell.

Yea, I wouldnt put too much stock in any of the 5 series products. I used an FX5200 to play WoW on my old Sempron system, and could barely turn it up to 1024x768. If you have to stick with the 5 series, go 5700, but I would suggest at least a 6600 or an x800 or greater, plenty of older low-cost cards that will meet your needs but not be useless like the 5 series.