Home Base in Tuscany or Umbrio

I haven't been to Italy since 1983 when I went on a European backpacking trip with some buddies, and in Italy we only say Milan and Rome. Now, my wife and I are planning our 25th anniversary trip to Europe for a month and we want to spend about 1 week in Tuscany or Umbrio. I am not familair with this area at all, and all I know is what I have learned from watching Rick's TV shows on this area and I have also listened to Rick's radio shows on this area as well. It has me captivated and I think it would make an ideal 1 week stop on our trip, sandwiched between two more active/busy parts of our itinerary. So my question is, what town or countryside area would make the ideal home base for exploring Tuscany or Umbrio? We plan to rent a car as we want to explore this area with the freedom that a car offers. We are also are interested in staying at an Agriturismo as well, but we are open to anything at this point. Any advice or suggestions anyone has would be apprecaited. Thanks