Best location to rent a car for touring Tuscany Hill towns after Amalfi coast?

I would first compare the train time and drive time to see what you save--it's right at the flip-a-coin mark for me. It's a lot of variables, but that is the best way to know exactly what works for you. Compare trains to various cities to choose the easiest stopping point with a rental car option.
If you do rent the car in the south, pick it up at the airport (not in the city) or in Salerno.
Depending on your flight departure time, you could stop somewhere closer to the airport--some of the places with Etruscan heritage like Tarquinia sound interesting.
If it is an afternoon flight, I would just drop at FCO.

Thanks. FCO departure is 12:50pm so sounds like you'd recommend dropping rental in Tuscany and taking train to FCO.

I dunno--getting close (like within a couple hours) could make for an easy morning if you have a night to play with. I am really fond of that southern corner of Tuscany if it can put you within the distance you feel comfortable for a morning drive to the airport.

I would pick the car up and drop it off at Hertz in Orvieto. It is about 90 minutes drive into Siena--all motorway and 4/lane highways.
Tuscany is best seen from behind the wheel of an automobile.

I would pick the car up and drop it off at Hertz in Orvieto. It is about 90 minutes drive into Siena--all motorway and 4/lane highways.
Tuscany is best seen from behind the wheel of an automobile.

I would pick the car up and drop it off at Hertz in Orvieto. It is about 90 minutes drive into Siena--all motorway and 4/lane highways.
Tuscany is best seen from behind the wheel of an automobile.

Thanks. Thinking perhaps taking train Sorrento to Orvieto, pick up rental car there then 4 days later dropping car in same location taking train Orvieto to FCO.

Thanks David. Agree with your plan.

A plan so good it's worth saying three times! ;-)

Why add the train? We did the opposite. We wanted to go from Spello, Umbria , farther than Siena, to Naples. It was easier and cheaper to drive on the autostrada, dropping the car off at Naples airport. The drive was so easy.No schlepping luggage on trains or going into Rome.

OK Thanks Suki. Any ideas for a convenient place to rent the car easily accessible from Sorrento? Naples airport? other? Thanks again. Peter

I just rented a car through AutoEurope from Europcar on Monday at the downtown Naples office and it was easy getting out of town without having to go to the airport. The office is near the train station and the Circumvesuvia line, about a 10 minute walk. I’m now in Orvieto (Hotel Duomo is great and has parking available) and will be driving to spend tomorrow night at a small hotel with free parking in Fiumicino. Sunday morning I leave the hotel, 10 minute drive to the airport where I’ll return the car. I did this last year and found it very simple not having to worry about trains or luggage.

Philip, thanks very much for your suggestions. I'm so used to taking trains & buses in Italy, I didn't consider the driving option but it sounds like a good alternative. Peter

Rent in Sorrento. Europcar, Hertz, Avis have offices there.
I don’t see the benefit of 4 people taking 3 trains (with luggage and all) to Orvieto and Chiusi to pick up a car, which can be rented right there in Sorrento. Renting in Sorrento is by far the cheaper and more convenient option.
Return at FCO if you don’t visit Rome at all. Otherwise return in Rome before staying in Rome. You don’t need a car in Rome.
You should sleep closer to the airport the night before your flight. Tuscany is too far for my taste. S..t happens.

Roberto, thanks much for your suggestions.