I've been using the Z7 for quite a while now, paired with my PHA-3. At first, I really didn't think the PHA-3 made a difference that justified its asking price, even though I only paid just over half of the Australian RRP of $1,099.95. After having used the pair for some time now for a range of things (watching netflix, movies, gaming, general music listening) I think the combo is really outstanding. Maybe it's just buyers bias wearing down my resolve but the PHA-3 seems to help with the issues people had with the bass - when listening to the Z7 through my ZX1 and other less powerful devices like directly out of my PC's Xonar D2X or straight out of my phone, the bass felt boomy and a little muddy at times - but all that has essentially been mitigated since I started using it with the PHA-3. Much more definition and composure in the low end now. I mainly use them balanced out of the PHA-3.
The Z7 is great for gaming - the "3D" soundstage that people are referring to does help place sounds while gaming in the right directions, and there is a suitable heft to explosions and punches and the like. I've been playing Batman: Arkham Knight and Borderlands: The Pre-Sequel recently, and both sound great. I've listened to a wide range of music through them, from James Taylor to Slipknot, Green Day, Joe Satriani and everything in between, with an assortment of jazz and soundtrack stuff thrown in for good measure (the Halo 2 Anniversary OST is outstanding, by the way) and the Z7 handles everything I have put through it with gusto. I've also been watching House of Cards at night with these (hardly the most action packed show I know) but I find it's actually very good for this - the balance for voices over background and ambient sound is great, and they perform much better than my speaker setup on my PC for this, which is handled by a pair of AudioEngine A5+ for front left/right, and Apple HiFi for center, and a pair of AudioEngine A2 for rear left/right, although it's only the A5's firing while I'm watching netflix.
Overall very happy, and happily reporting no buyers remorse after months have passed. Can't comment on any other headphones as the Z7 is really the first higher tier over ear headphone I've ever owned.