6'0" and I ride a 61cm Litespeed M1. It has a relatively tall HT-- not huge like a Roubaix, but taller than bikes like a Tarmac.

I have a long reach. I would look pretty 'pro' on a 56cm bike with a 140mm stem and a lot of seatpost showing. Instead I choose to ride 58-61cm frames.

Everyone's body is different, but if you're far outside of norms maybe you're not on the right size.