I think this hobby is not just about having some good measurement and fidelity alone, many factors need to be considered( how do we measure warmness, brightness, soundstaging, imaging, clarity, and how do we tell enough is enough ? I think only the listeners can decide how much of the "good things" is enough for them ).
Warmness, brightness, and clarity (i.e. a lack of "muddiness") can all be measured easily. Those are descriptive words that we, as a community, have agreed to assign to certain frequency ranges. As to whether "enough is enough", that's the point of this thread. We're being asked where our "enough" lies, if there is such a thing.
Imaging and soundstaging are more difficult to quantify, but not impossible. Something like the Smyth Realizer can make imaging monsters out of standard closed headphones, so clearly it is not a quality innate to certain headphones. Headphones that move the driver in relation to the ear (like the Sennheiser HD800, Stax Sigma and AKG K1000) do so for a reason, and it works to varying degrees.
All in all, I think there is a lot more "personality" in this pursuit than there should be. People striving for a sound that suits them are chasing a moving target. As critical listeners, we should be constantly growing. If you're trying to hear what's actually there on the recording, you want to do it with the best possible equipment. If you're looking for playback equipment to suit your mood or accentuate characteristics of certain music, you're collecting special effects. That, to me, is a different kind of hobby.