Globus is a wonderful company and I have traveled with then several times. I have a river cruise booked with them for next June already.
Globus has a coach tour called Leisurely Italy that is 11 days and spends 3 days in each of the cities you want to visit. The tour # is LK. I'm sure you would really enjoy traveling with Globus.
I strongly suggest that no matter which company you go with that you spend a minimum of 2 days in each location. I know that from experience.The 1 day in each place is just to tiring and not enough time to see anything.If you look at the reviews on these boards I think you will find that Globus is the favorite for many people.
Italy is very warm in the summer so either go in early summer,May,June or in the fall. Never go to Europe in August as many restaurants and other sites are closed. The Europeons take their vacations in August and the lines are long everywhere during August. With Globus you don't have to wait in lines but it would still be a problem with shops being closed etc.
This web site really does discount the price of the tours. I wish I had found it 4 years ago!!!

I made my reservation for the Globus River Cruise by calling the toll free # on the top and got a GREAT deal!!!