Here is an idea for you when / if you decided to buy used... or in general for the roadie...
Contact a local bike club. Preferably one NOT associated / sponsored through a lbs (biased opinion)...
Ask whose the best fitter in your area... sworn by all members of the club, who resolved pain issues riding, etc. Seek that person out for your correct frame size, and ideal geometry.
Research and ask around about what your needs are. Maybe there might even be a way to post a "wanted ad" with the local club? Peeps a lot of times want to upgrade and need $ to fund new.
Hopefully a bike from a local who dearly loved it would be in good shape, honest seller etc.
I could have very easily sold my too big of old road bike to my best GF. Who is also my size. She didn't think riding it too big would be that big of a deal since she wasn't going to ride as long as me etc. No way could I do that to another biker. I hope my thoughts are shared in the world for someone like yourself buying.
Btw... I *almost* bought that Trek FX. Actually, a couple pals kept pushing and pushing it on me. Something was not right. 20+yr vacation from riding a bike for me. When I finally found a drop bar road bike to ride... I felt just like a kid again on my old steele 10speed. THAT was what a bike was suppose to feel like to ME.
Good Luck... OH, and yea... you can never have too many bikes:cool: (being a TE member that is:p)!