Bottom Bracket Adapter for Cannondale Synapse 2?

Quoting the Cannondale website:

"Because the Cannondale SI Carbon crankset seamlessly integrates an
oversized bottom bracket shell with an oversized spindle and carbon
crank arms, you benefit from a direct transferance of power that
produces greater velocity while riding, and a crankset that is lighter,
stiffer more efficient than Shimano's DuraAce."

I understand that if you want to use any other crankset with this bike
(eg., a triple instead of the compact double it ships with, or Campy
instead of the stock made-by-FSA) a special Bottom Bracket Adapter is
required to (correct me if I'm wrong here) "fill in" the extra space of
this oversized bottom bracket shell.

My question: does anyone know if this Bottom Bracket Adapter will
compromise the performance of the bike to such an extent that it would
mitigate any of the advantages of converting to a triple or a Campy
crankset? I'm concerned that by replacing the stock spindle I may be
eliminating one of the features that makes the bike so appealing in the
first place.

Thanks.