There is a great difference between the music in those historical categories
For myself, I prefer listening to baroque, but I never play it because my instrument didn't exist then. So I play classical, 20th century and contemporary classical music.
John Philip Sousa.. I would definitly not categorize him as classical. No way. I would probably just make marches a special catergory. Or maybe as "national" music, since many marchces are a big cultural thing for the country they're composed in. Take the Internationalin and the National anthem of the former CCCP.
But I would put marches in their own category, just like rock, pop and rap.