Hmmmm, spending 2. :)
I will be posting my suggestions for an itinerary, based on what I did myself which turned out to be a very good experience: First, I would suggest finding a beautiful small town or village to stay -or two, depending on how much of a driving lover you are- rent a car and make day trips from there and then spending 2 or 3 nights in Florence -get rid of the car as you arrive there. My option was Colle di Val d'Elsa, its old town is located on the top of a small mountain -you can actually take an elevator to get up there- which has a lot to see and great restaurants.
|Colle di Val d'Elsa|
I would suggest to fly to Firenze -more centrally located for the route- or Pisa, pick up a car at the airport and start from there.
In my itinerary you will be visiting Siena, Monteriggioni, Montepulciano, Pienza, S. Quirico d'Orcia, Bagno Vignoni, Abadia di S.Attimo, Montalcino, Arezzo, Cortona, Lucca, Pisa, Volterra, San Gimigniano and Florence of course.