DON'T get the 7800GS AGP. It's almost exactly like a 6800 ultra. Not impressive at all. (Though the 7800GS's average framerate is higher than the 6800U's, frame rate diagrams show little differences, except in BADLY coded pixel shaders (F.E.A.R.'s soft shadows)). That, and the colors produced by nVidia cards are cartoony when compared to ATi's...
Edit: And you went and ordered it already. >:O