Having had the MDR-1AM2 for a few days now, I can say I am nothing but happy.
It does everything I throw at it, from thrash metal to japanese art music. What's very interesting is how loud it can play without sounding congested but still clean and each instrument separated, even the deep bass can play extreme loud without loosing definition. Also, the slightly overblown bass and high resolution makes these very well suited for low listening levels.
But, it's hard to not go loud, because it sounds good all the time. That's a testament to the very low distorsion. It's hard to understand how loud it is. Nothing is sibilant, nothing is harsh. These cans are fast, and powerful, hard to believe considering their small size and light weight.
As a active musician myself(electric lead guitar/classic 70/80s rock coverband using mostly Marshall 4x12s and/or Helix) it is very interesting to play Youtube videos recorded live in diverse studios, the instruments usually sounds very much like I remember ours from rehearsing and playing live. In example, listening to a closeup of a drummer showing off, it sounds much like when standing beside our drummer IRL. Impressive.
Recorded/Mastered music isn't the same thing, as it can be mixed/mastered to sound like pretty much anything, not doing well as a "real life" reference. Recorded/Mastered can sometimes sound the best on gear which is far from audiophile levels. These Sonys are much on the audiophile/live reference side of the spectrum, exactly like Sennheiser HD600 is.
edit. Oh, I forgot, electric guitars(well acoustic too) sounds perfect heavy distorsion or clean. The "hardest guitarsound" for a can to sound good on is distorted guitars, these cans do it, all kinds of distorsion sounds just great.