In 14 days you could develop a nice feel for Rome and Florence. 4 days in Rome and 1 day split between Pisa & Lucca (in fact in Pisa you can take an enjoyable walk from the train station to the leaning tower and walk by the school where galileo taught, etc). spend a day in Siena and perhaps a day in San Gimigiano. You could take a day trip to Pompeii (2.5 hours by car). I'd skip Naples entirely. Sorrento is pretty but so overrun with tourists that it has lost its charm. Spend the rest of your time in Florence.