This is probably better suited for the Graphics and Displays forum, and a mod can probably fix that, but I will try answer your question for you here anyhow.
The quick answer, is probably not. You should be able to replace the power of the 9800gt for about $100, but probably not a sizable upgrade. Since the old one is dead and you need a replacement, just go for best card you can afford. If that budget can be stretched a bit, a 5750 might be a solid choice for a decent upgrade, or even a 5770 (which matches/outperforms a 4870).