What's your inseam?
Mine is 29 inches and I ride a 13" 7.2FX.
It fits nicely.
The LBS close to you sounds like a good place to do business. The other one is probably OK too, the kid just wasn't a good salesman.
Mebbe ask the guy at the good LBS if he has anything comparable to the FX in function and price?
The bike will perform as well as you do.
If I buy a Madone it's not gonna make me the best rider in the club
Buy the bike that makes you happy, the one you feel good on.
That's the one you'll ride.