Hi - it sounds like you're going through just what I did in October. I wanted a new road bike, test rode the same ones you did, and got a good price on a 2012 Synapse (with 105 components, though). I will suggest when you test ride, wear your biking clothes! I know it sounds obvious, but I wasn't really planning on bike shopping that particular day. Long story short, I have a new Synapse. I'm shorter than you, with a much shorter inseam. The bike is a 48cm and just this morning, while speeding along on my trainer, I pretty much decided the bike may be too big for me. Ever since I brought it home from the shop I've questioned my choice. Don't get me wrong - it's a good bike. I'm just concerned about the fit. So, if you happen to be in central NY and want to check out a Synapse w/105 in 48cm, drop me a pmI think the 48 will be too small for you. Good luck, take your time, and try have fun while shopping (takes off some of the stress). Welcome to TE!
ETA: I just noticed that you posted under "New Riders". Are you just new to road riding, or biking in general? And what kind of riding do you hope to do?