Want to upgrade GeForce FX 5200

[Liverhead28]

Dell Dimension 4600 Pent 4 2.6 gh,
1 G RAM
I would like to upgrade my paperweight of a GPU, and having an old system I only have AGP slots. I think this - Radeon HD 3850 512MB 256-bit GDDR3 AGP - would be a compatable card but I dont know if bottlenecking would be such a problem that its not worth the upgrade. I know anything would be an improvement, but I dont wanna drop a race engine into a lawnmower. I just want to be able to play a few new games until I can get a new rig. Pls help

 

[Trotter]

Your CPU will e a little slower, but livable. You will have to replace your PSU, though, as the 3850 requires a minimum 450W.