You could do a nice theatre and beach vacation in Sydney. I have.
If you go 'in season' you can factor in music, opera and dance and then you'll be really pressed for time to hit the beaches where it could be a trifle chilly anyway.
As for the US, I look not just at the road houses, but the resident theatres as well. This would make Boston, DC, Chicago, Seattle, SF and LA pretty good. New Haven/Hartford has two road houses plus three major regional theatres and Goodspeed. That's a good standard for two small cities.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher