I ran into the same thing when I was shopping, it WAS overwhelming. The more I rode the more I narrowed it down. I went with a 2010 Roubaix Comp and have been very happy with it so far. Not quite a month and 200mi on it, so take it for what its worth. My LBS factored into the formula as well. Being new to RB's I wanted a helpful shop. I have been very happy with the LBS as well. FWIW, if the LBS had sold Treks I probably would of went with the 4.5 as I liked that one as well when I was testing. But that dealer was 1.5hrs from home, round trip.