I was in Italy for a month in July. My friend and I did a lot of pre-work finding hotels. We used various websites. For Florence, we got a great rate at Hotel Brunelleschi. Great hotel, right near The Duomo. The rate we paid was much, much less than the rate on their website and we paid in Dollars, not Euro.
Point is, if you have time, try all the different hotel booking sites you can find (I'm not sure if I can post them here.)
BTW, I would spend some time in Lucca. Beautiful small city and close to Florence.