Pros: Neutral, clear, subtle, comfortable, affordable, outstanding sound quality when properly driven.
Well I'm kinda new to Head-fi & since I'm a big fan of the HD600 here's my personal review of them which also touches on the amps & replacement cable (only mention it not analyze it). Here goes :
What I enjoy the most out of the HD600 sound is the balance & clarity. Right now I'm listening to Jeff Beck, "Blow by Blow" c1975 (produced by George Martin). My sources are : TEAC PD-H600 (PD-H600 uses the Burr Brown PCM1796 D/A converter, a 192kHz/24-bit component) & Kenwood KA-8006 (70WPC) vintage integrated amplifier (1974); the HD600 replacement cable is from Headroom, Cardas Fatpipe cable for HD6XX.
The sound is simply exquisite. I was listening to the album with my HD650s previously and the difference I noticed immediately when I switched to the HD600 was the forward clarity of the cymbals & ping sound with no roll off (sibilance free) while simultaneously hearing all of the other instruments & nuances, perfectly balanced; some in the background but never overwhelmed. My amp is set at it's most neutral possible i.e. the loudness option is never activated; I only put the emphasis on the filters to bring out the subtleties when I'm listening at a reasonable high volume.
This set up which is about all I can afford works wonders & truly makes the HD600 perform at it's peak. They never sound coloured at any time. As for the lack of bass or sub bass mentioned so often, let me just say that I can feel the bass in the sound as well as hear it i.e. the bass drum is felt & is always there & it's a special kind of subtleness by which I mean you can't miss it and I believe these headphones were designed this way in order to capture every sound possible without any over powering bass/sub bass or added treble/sibilance. Again, when properly driven the bass sound/feel is unmistakably present. It's quite ingenious when you consider it. I've owned the HD800 in the past & I still prefer the HD600 overall. I'm not saying they are better or dissing the HD800 but merely expressing my personal preference. I've owned the HD600s for over 10years (the ones I'm listening to now are my 2nd pair) & I have always come back to them eventually. When I put them on after having put them aside for a while and turn the music on they never fail to bring a smile on my face & a nod because my ears & brains are saying to me : "Ah yes, good ol' 600s, they've never let me down" They're like an old pair of slippers which you can wear all day/night in complete & total comfort.
Sorry for being long winded : to my ears YES they are neutral & thus permits me to adjust them, tweak them ever so slightly with a good amp to bring out the best of them & that's when they truly shine with any genre of music.
Neutral AND subtly adjustable with proper source = makes them shine.