a 6x9 cone is oval, not round, so, the g-forces of the oval cone being retracted into the frame, are going to deform it slightly, not only that, its going to deform irregularly to the rest of the cone, where as, every angle on a circular cone will contract together, making it more uniform and less distorted. also, a good amp will help out with distortion, but a 6 1/2" speaker will always have more potential to be more accurate than an 6x9. as for your question, for sheer SQ, boston acoustics is definately one of the dominant brands, pretty much every product they make in its respective class is at the top of the SQ list. can't go wrong with them.