Couple of words about metal music + D600.
(Summary on impressions on metal + 37 cans is here http://www.head-fi.org/t/715478/headphones-for-metal-music-ultimate-solution)
By far one of the best cans at middle level. Comfortable fit. Wide, very wide soundstage (for closed headphones). Powerful bass, but alas not well controlled (bass kin of hang out on the wide soundstage). Highhs may become too bright on the bright DAC/amp, no complaints on the on a neutral or dark gear. Overall a bit too sweet sound character, has a tendency to embellish, to apply "Photoshop effects" to sound.
Death: A sea of fun! I’m not sure, that Death should play soy joyfully, but when D600 play – they generate the most diverse emotions. Thanks for that.
Black: Well measured heavy bass (unlike on a number of other sub-genres) – the key to success.
Doom: Technical potency (yes, yes, again it’s about of volume of bass, albeit imperfectly controlled) coincides with the profile of the genre. Yes. They play doom. Savory.
Sludge, Stoner: Despite the overload on the bass, potentially unacceptable, D600 play Sludge/Stoner with more enthusiasm than their colleagues headphones on middle level.
Power: Probably the best cans for Power on the middle level (may be except AKG 712). Moderately lightweight and cheerful sound signature, nice midrange. Swollen bass is trying get in the way, but fortunately it fails to spoil the feast.
Symphonic: Slightly too brutal, but fun and cheerful anyway. Unintelligent, but entertaining interpretation of Sympho-metal.
That turns out not too well:
Thrash: Amorphous, bulky, slow. Characters of cheerful songs rotate in a tank with oil, wrapped in a soft protective shell…
Progressive: Fat and lard, looks like a greasy pan. Repulsive.
Alternative: Bass excess confidently leads the brain into the overdrive.
Overall, despite the impressive and apparent viability of a broad range of metal subgenres, D600 remain extremely non-neutral, non-flat and son non-universal headphones. Initial enthusiasm, if you are not full bore, is practically guaranteed. But how this enthusiasm will last, is much more difficult to say. Alas, for the cans with this level of "curvature", chances for close boredom coming are far from zero.