So, I went back to the lbs and had them find me a 60cm CAAD9 to try. I also took my 63cm CAAD5 so I could compare the two bikes and ride them back-to-back.

In the end, the two bikes fit me exactly the same. The only difference was a little extra seatpost showing and a few more spacers under the stem on the 60cm. The riding position - and top-tube length - were almost identical. If anything, I might have to go with a slightly shorter stem on the 60cm, as it had me just a little more stretched out than I'm used to.

I figure that my 63cm isn't too big, but neither is the 60cm too small. I'm going to stick with my order for a new 60cm CAAD9. Thanks to everyone for the help.