If you are considering going dual-gpu in the future, go with the 7600GT because an ATI card that can go Crossfire is like $300-400 (i think) where you can just buy another 7600GT later and slap that in.
Now don't go telling porkie-pies if you don't know.
The X1800GTO can do Crossfire WITHOUT any specialized card. Slap 2 GTOs together and voila, Xfire. So they both do that.
I am not familiar with how to setup Crossfire, i was just going from what I remember of the original Crossfire design, from the x800's