I am assuming, based on the price range, that you are comparing it to a CAAD. With that being said, I would think that you would be comparing it to a Large Ridley Fenix frame.
I would go try one out though since you said that your old CAAD was slightly too large. Sometimes the numbers given are not actual. My old bike was a 61cm but it was actually 58.5. Nothing beats going and sitting on the bike and riding it though.
I recently looked at the Fenix in an XL. It is an awesome bike and Performance has great deals on them.