Wow. This info has been incredibly helpful. Thank you all so much. I truly appreciate it.

So one last question... how about the Six -5?

Seems to be a blend of aluminum front triangle with carbon stays. the aluminum seems to be Cannondale's strong suit in this price range, and with carbon in the stays for a bit more "road buzz" dampening. It would also mean getting an ultegra RD (not that an amateur like myself is going to notice).

Based on everything I've read, I'd lean away from the Six carbon bikes. but would the six-5 be the best of both worlds? or perhaps the worst of both worlds, and I should just stick with the CAAD9-5?

Edit to add:
It seems that a common complaint about the Six is that the fork is too heavy. According to C-dale's website, the Six has the same fork ("six ultra carbon") as the CAAD9. Why don't I hear people complaining about the CAAD9's fork?