Oooh, wait, are we talking AGP?
In that case the 7600GTs are hella expensive!
7600 GS might be better.
It's not so much the speed or the memory, it's the entire package. The 6800 series just has a weaker core. The algorythms for computing FSAA, Aniso, and all that jazz are better on the 7000 series.
But, If you rule out the 7600GT then it's a matter of taste, I guess.