Good question. My own impression is that what is desired is a flat transducer and an amplifier/pre and transport that can deliver a flat response. However the source material need not be flat but aesthetic. We humans focus on the midrange. The human voice and its sonic counterparts are genetically programed. The midrange is the message. If the midrange is not delivered well we will not like it. Therefore it is all in the mastering, isn't it. A talented human neural network knows.
That is what is meant by a "wire with gain". For me personally, with decent source material, the best electrostatic phones and best driver interest me. I personally cannot afford the best available floor speakers, amp, pre, and turntable the world has to offer. It may however be possible to have the best headphone / amp system in the world. Stay tuned.