Good question. Well, my response is a bit late, but at least it is still true

The headphone I would like to have (but probably never will) is the HE90.
I own almost every Stax model in what I consider to be the golden era of development (1975-1998)
But the normal bias SR-Lambda (1979) is always going to be my favourite.
The flagship models play a different style, this model is a more impressive achievement, bringing high-fidelity audio to the masses.