I am 5'6" and ride a 52cm Trek 5200 carbon road bike. I was in the same position as you, and bought a Surly CrossCheck frame sight-unseen. My frame choice was based on comparing my road bike geometry to the geometry listed on Surly's website. I ended up with a 46cm cross check frame and it fits me perfectly. I have an ultegra triple group on mine, with Avid Shorty brakes, eggbeater pedals, and Bontrager Extralight wheels. It weighs in at just under 20# and makes a great road training and touring bike. You need to look at the standover height, and most importantly, the EFFECTIVE top tube length (the frame has a sloping top tube) when comparing to your road bike. It is easy to end up with a cyclocross-style frame that is too high and too long.