Thanks guys.

Kirsten, that was very informative. The Syanpse I'd buy is carbon. The CAAD is aluminum. My previous bike, which I had to return because it was way too small, was a race bike (2008 Cannondale Six13). It gave me golfer's elbow but I don't know whether it was the aggressive position or the the fact that it was way too small for me (it was a 40cm and I take 47/48cm, what was the shop thinking???).

I don't want to let a very aggressive position turn me off the sport but I want the option of being able to get into an aggressive position. It's a catch 22. I'm pretty sure at this point that I will go with the Synapse 6 carbon.