Nvidia 6800GS or 7800GS Best for Dell Dimension 8200?

[howfast]

I have a Dell Dimension 8200, P4 3.06GHz 533FSB with 1GB RDRAM. I am struggling with a Geforce MX4000 graphics card and am considering upgrading to run some of the modern games.

However, I am stuck with an AGP motherboard and as the windows [pardon the pun] for new AGP video cards appears to be closing with every manufacturer moving to PCIe format I am wondering which is the best upgrade path for now. I only installed extra RAM and upgraded my processor to 3.06GHz with HT [thanks eBay] before Xmas last so I want to hold on to this system for a while longer.

Has anyone tried the new Nvidia 6800GS or 7800GS cards in their Dell 8200 system? Any recommendations as to which is the best upgrade for a 3.06GHz system?

In particular were there are problems running either card with the Dell stock 250W PSU?

[blacknight]

I just got an Nvidia GeForce 6600 with AGP for my own desktop and it works fine (once I got a power splitter!)