to put 105 on the caad9?
The caad9 is a great frameset that (if I have heard correct) is stiffer than the 10, but a little bit heavier as well. tiagra v. 105...I have had both and once they are broken in....they both shift pretty much the same lol. I wouldnt worry about a bike that has tiagra.
My only criteria for my next bike, which will be a commuting bike, is:
Integrated shifters.
If I had tiagra on my caad10 I would not complain.