Tiagra components are fine. Ignore the components. The only decision there is comfort, and you'll have 4 options:
* Sora (Shimano's low end) -- it has a poorly placed thumb shifter, some people don't mind
* All other Shimano
* SRAM - You won't see these on the low end.
* Campagnolo - Hard to find where I'm at, only ever seen it stock on Bianchi.

You can probably just ignore components, I think. Buy the bike that you most enjoy riding and can afford.


Oh, and what garysol1 said! Very important. There is no deal when it comes to bikes. You're not gonna get more bang for your buck because a Trek or Specialized is better. You might because Trek happened to pick geometry and sizing that fit you better, or because their dealer did a better job fitting the bike.