I've owned my pair of MDR-V6s for 4 years now, and I absolutely adore them. They were my entry into headphone collecting and headphone repair. They sound amazing, everything is crystal clear.
I've tried a lot of headphones as well. Things like MDR-V600, V700, V900/HD, SHP9600, Superlux HD681, Grado SR60, ATH-M50X. And now I've tried HD 599s and HD 6XXs... And my V6s STILL sound better than all of them. That can't be right.
Nicer and nicer headphones close the gap, but nothing does it like my 7506s and my V6s. Some have bass that sounds as good, some have mids that sound as good, some have top end that sounds as good... nothing has the whole package.
I'm just so confused... each time I go into a pair of headphones finally expecting to have something that makes me say "wow, this is better than the MDR-V6." And then I go back to V6s, and they sound better.
Endgame is a state of mind.