I can't say I am not happy. This is by far the most incredible bass I have ever heard anywhere. My buddy who bought M100s a few weeks back can't stand the fact that even with those and an SVS, he doesn't have anything close to what I have. He doesn't have it bass-wise and he doesn't have it in terms of spatial extension, imaging and resolution. Dynamics, even at lower listening levels, are also better. It's just so effin' good...OMG!
Nonetheless, the 600s go deeper than the 500s. It's not subtle. That additional extension makes a difference even with music (I really don't care about movies because it's already more than good enough). It's the resolution. You can hear it in the growl of a bass guitar or the thwack of drums.
Admittedly, I don't fully understand why this is. Certain drums have very low subharmonics and those subharmonics are sometimes enhanced by the recording engineer. But string bass doesn't have harmonics I don't think. There's something going on though that I don't understand because bass and drums sound better on the 600.
