This is a great idea on there part.
They pretty much modded everything so there fabs had very little work on changing systems.
9600GT = Improved G94 > 8600GT > ATI 3850
9800GTX = improved G92 GTS512 > 8800GTS 512 > ATI3870
9800X2 = duh! > 8800Ultra > ATI 3870X2
I don't know about improved... my 8800GTS G92 scores about that high in 3DMark06, and I'm sure I have a good amount of overclocking headroom left.