Thanks for a wise answer. Unfortunately, over-analyzing is in my nature, but you've reminded me that it's not always a virtue.

I think I'll go to another LBS that has both Trek and Canondale, so I can compare them both, while looking more at the Specialized at the first shop. Either way, I'll have to give the most weight to how well I think they'll do at fitting the bike, but also to easily it will be for me to adjust things myself, or replace nuisance items. And as much as I like REI, and their willingness to let me try out several bikes while having to adjust stems and seats for me, I just don't get the sense they'll do a complete job of fitting the bike at the end.