I'm kinda partial to Specialized bikes. The Tarmac and Madone are very good pro-level bikes. Problem is (and this is pretty subjective) that I've heard horror stories about the bottom bracket breaking on the Madone. Obviously, check for stress signs if it's used. But for me, I like Specialized because they are stiff and easy to pedal without your hands (when you need to sit upright and rest). The Treks that I've ridden have had a bit more flex than I like.