I test drove a Suzuki Boulevard C40 (600cc) and I liked it. Belt drive is smooth and it kept up on the interstate with minimal vibrations.
I am 5'9" and 165lbs. I know that today, most bikes are much more balanced with a better center of gravity.
But like I said, If I know I'm gonna be doing 300+ miles a day, I'd be better off on an import. I may just have to get a Harley at some point later AND a touring bike now, but I want to ditch the Rebel for sure - It was a learner, and a good one at that.