Very hard to decide, as Florence is full of incredible accommodations and the definition of romantic or luxury varies a lot from person to person.
Americans (for example) like to stay in a place with all facilities ( air conditioned, tv sat, pool, spa etc ), That’s right , the holiday is sacred I say! This inflates the prices of some hotels, rendering them less attractive, especially during the hight season ( April, May, June, July, September, October, new year ) The hotels gather about 75-80% of tourist. While most people do not know that the Apartment or Bed & Breakfast is more cheaper than a hotel, but it’s still very romantic and full service all inclusive!
Or even in more ‘niche’ places such as Four Season Hotel or St. Regis Florence Hotel (which are maybe the best hotels in Florence or of the world ), have impossible prices Or even, Though Hotel Villa San Michele is undoubtedly gorgeous, you’ll find at least five equally beautiful and quieter places with world-class service. The prices are still steep, but significantly lower.
Try to have a look here: Terrazza Duomo Apartment
Or here: Pietrapiana Apartment
Or here: Signoria View Apartment
Or here: Le Terrazze Apartment
In an apartment you will have the opportunity to share it all with your family , to cook what you prefer to cook , to watch a movie together , talking in a living room or a roof terrace , or in the shade of a garden in the heart of Florence or inside a private pool for the exclusive use your
Have a nice stay in Florence!