Did a quick web search and came upon one of the top (and only) retail bike shops in Florence - Florence by Bike. It's a jam packed store with more inventory that most of us have every seen in one place (check out retail shop in top photo and rental/warehouse location in bottom photo).
Web site is www.florencebybike.it.
Service personnel are friendly and encourage browsing...that is, if you can fit between the aisles to shop! I didn't recognize some of the brand names, so was doing component comparisons in an attempt to understand the magnitude of the equipment.
Today, I shot the gap between the 99 cent store and 5000 Euro bicycles. Have to love the diversity in merchandise.
We're hoping to put together a bike excursion with students, so hopefully there will be another report soon.
Bottom line, if you're traveling to Florence, make Florence by Bike a must-see destination.