Terni, Narni, Carsulae

I'm also interested in Orte.

Have you considered Cerveteri/Tarquinia?
http://www.minorsights.com/2015/06/italy-etruscan-tombs-of-tarquinia.html
http://www.tarquinia-cerveteri.it/en/museum-and-necropolis-of-cerveteri/necropolis

Or Vulci? http://www.minorsights.com/2014/07/italy-vulci.html

Yes, I visited those places last summer- amazing!! I'm a little bit obsessed with excavation sites!

Those three might warrant an overnight. Check out Casata delle Marmore while you're there. It's an antiquities engineering marvel.

Thanks so much!

I'm assuming you've been to Ostia Antica. Have you done much poking around in the many excavations within or near the historic center of Rome? Places like Case Romane del Celio?

And what about the lower levels of many of the churches? One of the most famous is San Clemente, but there are others that are fascinating (such as San Crisogono in Trastevere) that few people have visited.