My limited experience (I'm 6'0", 225 lbs., 56 yrs old, inseam 33.5"):
I was looking for my first new bike since 1970 and decided on a CX bike. I tried a 2003 Lemond Poprad (57cm) that felt great. The components were low end, but the Reynolds steel frame was fantastic. I also checked out a couple bikes at a lbs sale - the main one I tried was a '04 Redline Conquest (not Pro) at 61cm. It felt exactly the same in terms of size as the Poprad with the exception of the top tube length which was a bit longer. It was a bit of a stretch, but I could have gone to a shorter stem to make it feel good. What surprised me was that the standover height and the overall feel (size-wise) was the same as the Poprad. I also tried a 58cm Specialized Allez that felt almost identical to the other two bikes in terms of size - it had a slope top tube, but measured the same as the Redline from stem to seatpost. Three different bikes, three different sizes, same feel size-wise. I ended up getting the Lemond because of the steel frame (the others were aluminum). No advice for you - just my experience.
Good luck, and have fun shopping!
Dean