If you want to do Tuscany, that does not preclude a day on Florence as well. The Tuscan countryside may require a car though. One place that is well situated for northern Tuscany and Florence would be http://www.villailpoggiale.it/
in San Casciano val di Pesa (basically one exit south of Florence on the road to Siena. It's offers good access to Florence (although with the ZTL now, one can't just do the easy drive in and I don't know what the public transport options are from San Casciano to Florence are), Siena, San Gimignano and Lucca. The towns are a bit of a drive but not unreasonable.

The villa is pretty nice with a range of rooms in terms of luxury vs. basic.