I'm having a hard time deciding between these two. I had ordered the 600's, and they never came in, so now I'm going to re purchase. Was going to try the Alessandro MS-1, but due the upper midrange fatigue of the Grado's I've had, I've opted to nix that idea. I'm looking for the best possible sound here without any harsh artifacts that will make me wanna throw them out the window. Anyone heard *both* of these, and any audible differences worth pointing out between the two, that are worth the extra money to lay out for the 650's? Thanks.