MygpuK,
I grabbed the quote below from your other thread (Cyber Snipa Sonar 5.1 USB Headset -- wow that's an earful!)...as I think it presents, to me, the key premise of your discussion.
"~~I'm a scientist, you know

I suppose there is nothing in this world being subjective, only tastes and biological "specials" of given ears which result in tastes also

We should just clear it out, when NOT using an amp, we must get a good_to_go (fully portable) product, which must fit our tastes."
Having owned several high-end audio/stereo systems at the same time (Electrostatics, Planars, & Dynamics w/Ribbon Transducers - all driven by high current/quality amps), I found that I enjoyed them equally for different reasons. Based on that experience, I would say that there is no such thing as 'one headphone for the masses'...why?
In the end, what I like in a headphone sound signature may not interest another as much as it does my 'tastes'. This has been going on for decades and will continue for many more! In fact, many of us listen to different equipment/sound-signatures based on the music genre, mood we're in, etc...did this in my stereo days as well -- The Who on Quad ESLs - yechh! Vivaldi...priceless!
One only needs to read the variety of reviews in this and other 'hi-fi' forums to understand people do 'hear' things differently -- most likely based on biological 'specials', as you put it, and also what I'll call sociological 'biases' (music genre tastes, pride of ownership, product design & branding, perceived value, etc.).
Some audiophiles may want the best measuring headphone, while others trust their ears to guide them...neither is 'wrong'. Hopefully, they are choosing to spend their hard-earned dollars in a way that brings them the most joy when they listen to music, watch movies, or are gaming.
Science has its place but it is just a means to an end...that said, I firmly believe that Headphone design / Transducer quality can impact the listening experience and is something I’m willing to pay for...if I can hear the difference.
As I'm walking down this road again with Headphones (instead of room-sized speakers), it's costing far less and I'm enjoying it way more! Further down the road, I expect I'll have a broad mix of technologies as I did before. For right now, I'm just trying to decide between rounding out my mid-range dynamic collection (880, 701, or 600) or splurging for the Holidays and getting an HE-500...whichever fork I take, it'll be fun.
Lately though, I've been spending more time listening to my $40 M80's on a Rockboxed Clip Zip than anything else. Just can't believe the sound I get for $75 out the door!
PS - which ice cream is better -- Chocolate or Vanilla?...Butter Pecan? Ben & Jerry's, Haagen-Dazs, maybe Jeni's?