Odd that you ride a 56. I used an inseam based forumula to compute that mine should be a 58.
I have a 29" inseam and a 33" "true" inseam. Plug that in to any of those and it'll spit out between a 56 and 58cm bike. I tried out a 57cm Bianchi that I really liked but went with a 56cm Surly due to price and fit. My next bike will probably be a Surly Long Haul Trucker that I will get in 58cm since the geometry on that frameset is quite different from the Cross Check.
I asked the guy, who was otherwise helpful, if there was a "break point" on pricing where you get great value, and he started at the $3,400 Trek carbon fibre model. 
Don't take this the wrong way but you were an easy mark for them. They probably figured you to be the typical 50s-ish guy in need of a thrill while you ride on the MUP - i.e. a needledick looking to slap on the spandex and "shred some hills" on Saturday. Obviously that's not you but that's probably what they pegged you as. I get the opposite when I first go to a bike store "for riders your size we recommend this [total low-end "hybrid" that all the fatties ride]." When I point out my bike outside they usually go "oh, well, have you considered a Cervelo?"
