I thought about that PalenQ. But depending where they are flying in from may or may not be a good suggestion. No way would I want to to "straight away" to Florence after getting off an overnight red eye from Seattle when I haven't slept a wink in 24+ hours.

You'll need to figure out exactly how much ground time you have once you reach Rome, 6 or 9 days or nights. If only 6, then you really should stick to only 2 cities and forget any side trips. 9 days will at least allow you for 1 extra city. What is your interest in visiting the Amalfi Coast in winter?

Like others, I would suggest either heading directly to Venice or Florence after landing in Rome, and save Rome for your last stop so you won't have to back track. You already know the days will be short and probably dark by 5pm at the latest, so a full day of touring is almost half of what you'd have in the summer, when it stays light until almost 10pm. It's discouraging to have to limit your trip, but by doing so, you'll be able to see things other than the roadside between cities on the train.

Find out what will be closed on or around Christmas/New Year Eve/Day, or have abbreviated hours, as this will have a direct impact on your trip.

Weather may or may not affect your trip, as others have mentioned, and it's not uncommon for transportation strikes to be scheduled.

Ah, the joys of travel!

Even though a tour could get you from place to place, there are big issues with it.

First, they have a schedule to stick to and no matter the weather, they can't shift things around as you can if on your own. Example: on a tour which stopped in Rome, during a walking tour, a storm hit and there was nothing to do but take shelter and wait for the tour bus. Had I been on my own, I would have changed plans, caught a taxi and headed to a museum, cafe or hotel room.

Second, travel will be on a bus, during the day when you could be seeing things. On your own, you can plan travel for late afternoon or early evening when it is dark. In Summer when days are long, I wouldn't do that, but in winter, I would.

Cities and even small towns can be nice in winter, but the Amalfi Coast is really not a good winter destination. Sorry to say, but it is not a good choice for this trip.

Fly into Venice and out of Rome or do the reverse.

>>Fly into Venice and out of Rome or do the reverse.<<

Should do -- but apparently the OP has already purchased R-T in/out of Rome

Yes big mistake many folks make - not flying open jaw - into one city and out of another.

<flying directly into Rome and departing via Rome>

I also assume that means air tickets already purchased.

I assume for Christmas they have already booked plane tickets - do things like ad-on fares still exist? Be great to fly into Venice then Florence - Rome - save money on extra trains and time.

If your dream is Venice, then take a train to Venice upon arrival and spend the first couple of nights there (you will be jetlagged upon arrival so might as well use that day traveling), catch a train to Florence for 2 nights with a 1/2 day trip to Pisa (only if it's a must see), end your trip in Rome. You don't have time for the Amalfi Coast. That can be your next trip with some other points south or Tuscany and Umbria.

Could be a fairly miserable first day -jet-lagged and schlepping into Rome Termini - a hectic station - with luggage - 3.5 hour train ride - get to hotel in Venice - don't sound like fun to me - I'd stay in Rome- previously I said consider going to Florence first day but re-thinking that - just stay in Rome first days then bop up to Venice and back to Florence and Rome last night before flight.