3DMark is not the end-all of a given GPU's abilities although I'll admit 3DMark06 tends to favor the red side.
My reaction to the GTS-SLi score: "Wow! That's pretty good!"
My reaction to the x2 score: "Sounds about right."
FRESH REFORMAT BETWEEN CARDS
A single GTS destroys the 3870x2 @ 1680x1050 ultra with 4x aa The single GTS gets 15 more FPS..