Tuscany base for 6 days

Look for agriturismos outside San Gimignano or the vicinity. The farms in Tuscany are very small, and virtually every one has apartments and/or rooms for rent. Booking.com has a bunch listed, as do a number of websites. Google "Agriturismos" jand they should pop up.
Last time we stayed there, we preferred to do most of our own cooking--and Poggibonsi has 2 big great supermarkets.
The region has crooked, but well paved roads and they're very well marked. We had no problem navigating even without road maps. A rental car is required to properlys visit the hilltowns. Don't miss Volterra.

We found Siena to be very congested and parking was very difficult to find.

We are two couples similar in age and actually doing the exact opposite in terms of regions and dates; but are traveling by car. If you can travel by car in Tuscany it will be much easier and time efficient, trains do not run everywhere so you would need to rely on buses.

I suggest Greve as a base which is where we are staying at a b&b for the week before you arrive in Tuscany, that is quite similar to an agriturismo. If you want to find an agriturismo nearby, google tuscany agriturismos and there are a number of sites; I also suggest you just start with the google map in the area where you want your base. As you zoom in the google map actually shows the agriturismos by name and then you can search for them by name. A couple of them we researched were Agriturismo - Patrizia Falciani, Podere Campriano and a friend highly recommended Il Casello Country House B&B. Greve is a small town within walking distance of several places to stay; has a chianti tasting center with more Chiantis than you can imagine, good restaurants etc. Also many fun things to do nearby, wineries (Vignamaggio - the claimed home of the woman Mona Lisa), the town of Lamole, short hikes etc. We have stayed in San Gimmy and, while amazing with the towers and all, we did not think it was as centered in the Chianti region as Greve.

You can easily get to the locations you mention; only Montepulciano would be a little further day trip (1 1/2 hours each way). You could combine San Gimmy (1 hour away from Greve) and Volterra (45 min from San G - 1 1/2 hours to get back to Greve) since they are both in the same direction.

In terms of the Chianti region (this year is the 300 year anniversary from 1716 that Medici designated the region), a little town 10 KM south of Greve, Panzano, has the last two days of its annual Vino al Vino chianti festival, approx 20 vintners in the Panzano area, on Sept. 17 and 18. We will be there the 17th; then off to Cinque Terre on the 18th. Panzano also has some agriturismos nearby but availability may be impacted by the vino attendees.

We are day tripping to Florence (using a bus there and hired driver-transfer to return that night). We are driving to Siena another day, which on the way there and back allows you to see one or two of the other small cities such as Radda or Gaiole, and possibly some abbeys or castles (google abbeys or castles in tuscany for maps and info).

I hope this helps and am happy to share any other information we have. Good luck and have a great trip.

Thanks for the info!
We will be renting a car while in Tuscany...we will be coming from CT by train..
I didn't know about the festival...we will be there from 9/17 til 9/22..hope it won't be too crowded..
We do have three accommodations on hold..One just outside Siena and two in Castellina Chianti area..
We are trying to decide which area...many pros and cons..

We have stayed in SEVERAL areas over the years and decided that if you love your agriturismo, you can't go wrong !

We loved Borgo Argenina in Greve because Elena offered a cooking class that included all of her guests...we enjoyed the evening comraderie after we drove back from exploring towns.

Where are the agriturismos located that you are considering ??