Art museums in Italy are generally expensive and crowded.
The churches are mostly free, sparsely populated, and filled with art as good (or better!) than what's in the museums. The churches showcase architecture, paintings, sculptures, and frescoes, all in one beautiful package.
Bonus points if your travel companion is an art teacher with 40 years of experience, knowledge, and stories! (Lauren said that whenever Jeff starts talking, English speakers begin following their group around.) ;-)