Valadelphia, You really ought to consider going to Florence sometime, since you say that you're 0 for 8.
Florence was so central to the Renaissance and the development of western art. There are so many churches there with so much art from the 15th century - the 1400s, and even earlier. Giotto, Brunelleschi, Ghiberti, Fra Angelico, Masaccio & Masolino, Ghirlandaio, Donatello, Bottecelli and Michelangelo.
Stacy - With a mere 10-11 days, you are going to have to make some choices. You don't need to hit the 3 pearls on your first short trip ... and indeed, time in smaller cities that are NOT among the 3 most over-run locations will allow you to experience a slower, quieter, more personal Italy. If you have time and scheduling ability to soak in opera in the north (Milan, Verona, Venice), Florence is likely more than you can include.
You could visit Rome and the Amalfi Coast and not much else; perhaps a day trip to Pompeii or Capri (or different island: Procida or Ischia). If you can work in the archaeological museum in Naples, your time in Pompeii would be enhanced.
OR, you could stay north ... Milan for 2 or 3 nights, one of the Italian lakes or the Dolomites for 2 or 3 nights, plus 2 or 3 nights in Venice and even one or two nights in either Padua or Verona. Probably in the reverse order. In to Venice and out from Milan. If Milan is your departure city, 2 nights should be adequate.
OR a Rome and Florence trip, but that would limit your time for smaller, quieter areas/towns/cities in Tuscany, or perhaps Umbria.
There are no "musts," other than taking the time to enjoy.