Concur with Sassafrass.

cb,
Good planning and a nice trip. Agree to still cut 1 day from the Cinque Terre and add it to the Tuscan countryside. Please don't hesitate to rent a car for this part of your trip. You will enjoy it so much more if you have the flexibility of your own car. Driving in the countryside is a real pleasure, super easy, and allows for photo ops and discoveries. Do rent a car!!! You can pick it up in Siena and drop it in Chuisi or Orvieto, then just train into Rome.

Buon viaggio!

What a great compliment! Thank you all so much. This has been such a great resource for me! I appreciate all of the help so very much! I couldn't have gotten this far without help on fodors. :)