CB650R is pushing 90HP on top of the powerband on 650CC which is plenty of bike for the power to weight ratio. Very cool naked, yes, more expensive & a more premium product than FZ's RN's and SV's.
400's are pretty cool but depends on your height, weight, and what kind of riding you plan on doing. If you just want to do urban crawling and dick around I'd go for a 400, even cross-shop ktm's or husky's.
I'd skip the 600 in the kawi line-up and jump straight to the 900 which has a well rounded I4. Tame and good low-end torque for city driving and super balanced for long highway rides and poppin powerwheelies. I think middleweights are just that, middleweights, most of the time, and always lack that little something, and that's just me, I drive a boring car but want more bike than I need.