At your weight a larger volume tire would only benefit you in ride characteristics...20's are abusive on all but the smoothest streets even at my 165 pounds. When I swap over the 23's the ride becomes much more buttery. Same brand tire, same wheels. Give it a shot.

Looking for a really smooth tire with nothing but supple ride quality and great grip in a 23? Gommitalia Calypso K's are heaven! I always ride the skinwall version and it's, hands down, my favorite tire.