Hey all, pretty new to road cycling. I got a Caad9-6 last year outfitted with Tiagra with the idea that if I liked cycling enough, I'd eventually upgrade. Turns out I love it. So I'm wanting to slowly upgrade (so the wife doesn't see the checkbook and murder me) to Ultegra 6700 components. Can anyone offer me suggestions on how best to do that? Are there parts that won't be compatible and are there places where I have to upgrade multiple components at the same time (ie, cassette and rear derailleur, crankset and rear derailleur)? Thanks for any help y'all can offer me.