If you want to do centuries the CAAD9 is not the bike for that so stay far away. And also carbon frames don't go "soft", so I don't know where you read that mumbo jumbo. The Pinarello is overpriced for what you get because it's a "Pinarello" so that leaves the Trek. Other than that also look at the following bikes:
Fuji Roubaix ACR 1.0 (get a red saddle and bar tape)
Cannondale Synapse Carbon 5 (red saddle and bar tape again)
REI has the Synapse on sale right now for less than your budget and it would be the bike I would go with above all others.