Finally took the plunge yesterday and picked up a new bike. A 2014 Specialized Roubaix SL4 Sport 105. I decided to go with the 54cm frame, based on the advice in this thread as well as several test rides on both sizes. So far I feel really good about the decision, although I still need to give it a proper test. In my opinion, it feels like a great fit, whether I'm on the hoods, in the drops or out of the saddle sprinting up a hill. Thanks again for all the great advice.