...thought it's Borat selling pizzas
Thought it was only me who instatly thought that this guy looked just like Borat 
...thought it's Borat selling pizzas
I would entirely disagree with you on the basis that electrical damping is essentially a fantasy (go ahead and tell me I'm wrong, and then go ahead and tell JBL, McIntosh, BK Butler, Rod Elliot, QSC, Accuphase, and so on that they're all wrong too). Damping is primarily (like 99%) a mechanical feature, and Grados rely on nothing but the driver itself (more or less) for this (and their drivers are good; I'll give you that); if you actually reviewed the CSDs you're blindly referencing (and you can actually go beyond purrin's measurements, and go look at CSDs from He&Bi and GE too), most of them (being Grado models) exhibit ringing in the upper treble (and FR and IR will also show this) - and believe it or not, some people just don't like bright cans that have resonance artefacts. And that ringing isn't really hard to predict based on the enclosure design. If you want to look at a "singularly well damped" example of a headphone, the Koss Pro4/A and 4/AA are good candidates. Most 'stats will also put up a very clean CSD too (because the drivers are extremely well controlled). They sound very different from Grados. And no, I'm not saying ringing is a bad thing by any means here (even purrin makes the comment that the RS-1 "look worse than they sound" on measurements). It's part of their coloration and their flair - and it doesn't suit everyone.
Their impedance is very stable, so changes in Zout won't result in any significant FR changes unless you increase Zout substantially (which will act on the bass region where the impedance peak is; here's a great article on the topic: http://en.goldenears.net/index.php?mid=KB_Columns&document_srl=1389) - what's really quite disturbing about your argument is in one hand you're taking the modern marketing line of DF as pushed by makers like Crown and Anthem (who are both miserable shills with a history of saying or doing anything just to close a sale), but you're then using that fallacy to argue against itself (and saying that DF is "bad'). Sure, high Zout *can* be a good thing depending on overall system Q (which is an unknown here), but we'd be talking about LF response based on the impedance of the Grado drivers (it would be most pronounced with the GSK and PSK). Basically you'd be talking about a slight bump to the LF as Zout went up; I can tell you from experience that going between 2 and 500R doesn't do much of anything, even with the GSK. As far as what happens if you over-damp (which you're not gonna do without physical modification) - it should not ever produce a "harsh" or "tizzy" sound (because that would be a result of ringing, which critical damping will prevent...) - it'll just be over-damped. And at that point they'll just sound dead and lifeless. So in summary, *IF* DF were worth phoning home about, it would actually REDUCE the harsh/tizzy sound (by better controlling the driver's movement), and decreasing it would decrease damping (which would increase ringing and tizziness (like I said, your argument is logically troubling)) - now of course in the real world that doesn't hold up, because DF isn't worth phoning home about, and all you'll get as you run Zout up is a slight bass boost (which I could see people interpreting as a slight warmth, but we're talking very slight). If you wanted to make them ring worse, you could EQ up the treble or get really nasty and setup a filter to target and excite the points at which the enclosures already want to ring (you'd have to measure them before you could build this) and they'd sound absolutely disgusting at the end of it (why anyone would want to do this to any headphone or speaker I have no idea, but it is theoretically possible). Now, if all you're getting at is "more bass compensates for their brightness" (either because it's changing phase response, or by masking, or a combination of both) - that's fine. But we have tone controls for a reason.
They're sensitive, stable, and low impedance - they don't want for much in terms of power, and you can get the same party from more or less anything that'll give up the power they do want in a clean way. Clean and quiet is king, only because I think a lot of people will have an issue listening to hiss or pot rustling inherent on a lot of the shoddier amplifiers out there. But as gradofan pointed out - good current supply, clean tracking, and you're pretty much set. If you prefer the coloration of tubes or equalization, or whatever else - that's a personal choice, and should be left up to the end-user to explore. I think I need to qualify that my statements are being taken massively out of context though (is it because they're hurting someone's bottom line I wonder?) - my comments were specifically directed at preproman's question, and based on the knowledge that he has a (very dapper looking) pair of D7000s that I'm assuming he has suitable amplification for. Whatever is driving those will have no issue driving any Grado. If someone wants to experiment with various tubed or non-tubed products on their own, that's their choice - and I provided a list of the four manufacturers I see most commonly suggested when people for ask a good amplifier for their Grados (which usually come from a more subjective "amps are all different" crowd and do include a combination of tubed and untubed devices) - as a starting off point. Of course there are many different amplifiers out there, and people will find enjoyment in a variety of products that may not be considered "right" by the mainstream - and that's also perfectly fine (but I still think having a starting point is helpful versus "go forth and frolic"). But I'm going to take an issue when you try to force everyone's experiences into some "grand theory of the Universe" to either explain your own experiences, or sell product.
"musicality or some engagement is a must"
my first place on my priorities.
"I haven't heard a Grado yet, but it's next on my list of auditions"
you will be amazed. tell me your experiments after the grado session.
"In terms of musicality overall I found Sennheiser the worst, I just can't get engaged with most of them",
agreed. even hd800 is non-music proof.
"Beyers can be a little lifeless but some are not lifeless at all like the DT 990 and I generally enjoy them"
nothing special here: only the bass departmen is raised a bit. that helps a littel bit to warm up the overall signature. but grado musicality I'm talking about here is something else. i mean TIMBRE.
"I always found AKG full of life, enjoyable, and realistic"
yes its technically a miracle to listen to a gitar solo in the left corner of the stage and at the same time the singer is in front of you.
but after you listen to grado you will say: i feel the spirit of the song. and that's the most important: grado can give you the best midrange as possible (most important in the FR) and the give you most accurate acustic instrumentation.
"The only STAX I listened to was a little on the boring side"
now thats a shame. but japanese ear are different - their whole line up is for their music their ear.
"The best, most enjoyable, most musical, and realistic headphone I've heard was the R10"
should be true. everybody is raving about R10's - sony is a mass product, it is specialized for the whole planet.
"I wouldn't dismiss amplification"
never sad that, I only wanted to assure you that I were listening to EVERY headphone with nice amplification.
"I can't comment on cables as I haven't experimented with them but I can see copper vs silver cables making at least some difference."
same: i used Van Den Hul line always -best cables ever - so that was not the weakes link in the chain.
"Different ears, dunno, but different preferences is definitely something that makes a difference among people."
piano should sound like a piano. gitar like a gitar. this is the point of headphone manufacturing.
"well it's recorded and mastered music"
you can easily make your decision for a well mastered violin (or not well mastered) if you listen through Grado.
"every single headphone is colored in some way"
yes but there are more colored ones and almost no coloration too.
"If audio was recorded and mastered perfectly..."
for example chesky mastering is pretty perfect. you shoud listen to these if you figure out which headphone is the most musical.
"realistic isn't everyone's goal or ideal either."
sorry i have to disagree. for example: DRUM
each type of drum head serves its own musical purpose and has its own unique sound -> this unique sound we want to reproduce on our mastering and on the membran of the headphone too.
