In the past I used to own the Susvara and needed to decide back then between them and the AB1266. The AB1266 was better suited for the music genres I listen to and my personal preferences so I chose them. But I was now able to get a new pair from Hifiman and wanted to share some experiences. Especially after I also listened to a lot of other gear in between.
The main characeristics to describe the Susvara are for me transparency, clarity and naturalness. That's what the Susvara really excels at. The sound representation is very natural, maybe the most natural I have listend to. But that also makes it sometimes a bit boring for my personal taste. The AB1266 for comparison is not really natural sounding, but makes the music much more exciting with raw details and an industrial timbre. Of course this is personal preference and differs from person to person and the music you listen to. Another point that stands out for me is that the Susvara "disappears" when listening to music. I noticed this especially after listening for a longer time to the Susvara and changing to the LCD-4z. I could literally hear the headphone construction due to reverberation on the 4z. Your brain adapts very quickly and you don't hear it after a minute or so, but I can reproduce the effect every time.
The main complaint I have with the Susvara is mainly the bass. The bass is present and goes deep down. But it is a typical planar bass. It really gets noticable with modern music and especially on tight beats which just don't sound like they should. No feathering, just dry bass. Anyhow, I generally think the Susvara is extremly well tuned for accoustical music, the AB1266 or LCD-4z are better suited for bass heavy modern music in my books. I'll definitely keep the Susvara for rotational listening, that's why I bought them again.
To also add some experiences to the whole amp discussion in this thread and to people who don't hear fleas cough
: Based on your listening levels you can also drive the Susvara nicely with smaller mobile dac/amps. I can drive to to around 75-80DB with 60% volume on the single ended output of the Qudelix 5K which is my comfortable listening level.