What AGP should I get for my old system?

Well Ive been reading since yesterday (using safe mode, coz i burn the card) about the benchmarks and options i can get for my old computer. I got an old system, tryin to get as much as I can from it, its a D865PERL mobo with a Pentium 4 3.00 ghz Bus speed 800 mhz Socket 478 with a BFG Factory OC Geforce 6800 GS 256 mb AGP 8X with the Foreware 175.19 drivers and 1 Gyg of RAM DDR320 DIMM.

Well the Geforce just died on me, i think i burned it, coz i didnt clean the fan since i got it. I open the cover yesterday and it was full of dust and dirt. Ok the point is, i need a new agp vid card.

I have check a few options from Newegg and another few from ebay. For what ive read, HD 3850 is the best AGP card still in the market. But for some reason, I read somewhere that it will be a waste of money coz my old processor will kill the card. I have seen a Geforce 7300 GT OC, a Geforce 7600 GT Oc and i found one Geforce 7800 GS and of course theres still a lot of ATIs around.... I still think that HD 3850 is the best option, but its still around the $140.00.

What I want to do is, to buy the best card to fit my old system, taking advantage of every resource i can get out of it. I know it wont be running like a Quadcore, but what i need is to make this old system as reliable as it can be done with the new AGP card.

Which one should i get?

Thx for the help guys!