Upgrade 7800GS to HD 3850 AGP

So i'm debating on upgrading my XFX 7800GS OC to a shiny new HD 3850 AGP... Now I know the whole get PCIE arguments and such, but my computer is pretty decent, and does have dual CPUs... I just was wondering if you feel the 3850 would be bottlenecked on this system or not, and what the best version of the 3850 is. I'm also thinking about splurging and getting 2 more GB of RAM. If I up the GFX I should get another cupple years worth of gaming outta this rig right?? (I'm also poor thanks to school so a complete rebuild wont be happening soon.)

Mainboard: Asus PC-DL (only AGP8x)
CPU- 2x Xeon 3.2GHz 2MB L3 cache 533FSB w/HT (SL7AE)
RAM- 2GB dual ch. Corsair XMS TWINX2048-3200C2PT
Graphics- XFX 7800GS OC AGP
Hard Drive: 2x WD CavSE16 320GB SATA in raid performance (Windows, Apps and Games)
1x WD CavSE16 250GB SATA (Swap file and storage)

Thanks Alot!