OK, I'm ready to go ahead and book tickets from Naples to Siena for this June. Someone (jules m?) had this to say the last time I explored this question:
I just double checked, and IMO, your fastest route is the high speed train from Naples to Rome Termini and then bus from Rome Tibertina (right next to the train station) to Siena.
I followed up on this, and I think he's right. I've looked at the bus straight through as well as the whole way on the train, and this one has only one change (at Tibertina) and takes the least amount of time.
I guess I want some guidance or verification here. I thought I'd have to get from Termini to Tibertina, probably on the Metro. But I just checked and there's a direct Frecciarossa from Naples at 8:09 to Tibertina, getting in at 9:42. Then there's a Flixbus leaving Tibertina at 10:15, arriving at Siena Gramsci just after 1:00.
These times are perfect for us. Does anyone see a problem here? Am I missing something? I want to go ahead and book, so I can stop thinking about this.
Thanks for being patient with me. I'm not usually a fussbudget, but for some reason this leg of our journey is bugging me.