I had a chance to audition the Susvara alongside the Utopias so I thought I'd share my experience.
The setup I auditioned on was on a Roon Player with 44.1Khz 16-bit music -> Aune S6 DAC -> iFi Ican Pro -> balanced output.
The Aune was outputting at a level of 85 to 95 and the iFi ICan Pro was between 12 and 3 o'clock.
To give you an idea on my listening background - I have Focal Clears being driven from a TEAC UD-503 in Active Ground mode from a balanced cable. I was really curious on the gap between Utopia and Clear which is why I auditioned. Many are drawing comparisons of the Susvara to Abyss Phi and Stax. I can't comment because I have not listened to either. Before the audition, I was under the impression that I was already reaching a point of diminishing returns with anything above the clear.
I was wrong.
The Susvara blew my mind. I've never heard anything like it before. It was so pure, clear, musical, balanced - and extremely transparent. I totally loved them. To me, it never made practical sense to go out of my way to get music files higher than CD quality, because I'd have to repurchase everything in my music library. The Susvara level of headphones really lets you get EVERYTHING out of your music files. The imaging, soundstage and that "air" were amazing. It made music styles/genres that I would never listen to, sound GOOD.
I thought had found my end game with the Focal Clear, but I didn't. My goal is to get something at the level of the Susvara. It truly sounded heavenly. With a Susvara level of cans, I could be content and then just focus on enjoying music instead of constantly upgrading all my gear.
Maybe the Susvara really do require crazy amping power to sound good. One thing I noticed, is if I cranked the volume from 12 towards 3 o'clock, the override protection would kick in and the unit would cut the juice until I dialed back the volume.
For comparison purposes, I listed to the Utopias as well. They sounded good, but nowhere near the level of Susvara. Susvara had a much lower noise floor, clearer, more separated sound. Not trying to put down Utopia - but they sounded mid-fi to me after Susvara.
From a sound quality perspective, Susvara is all I would ever need. In terms of the other common criticisms on build quality and price - there's probably truth to it. I think HiFiman probably spend most of the R&D budget to push towards that next level of SQ with planar magnetics, versus the design and build quality.
I found the design of the Susvara to be pretty streamlined - they are not as fat and bulky as other Planars and have metal construction. I prefer the shorter, rounder each cup shape of the Susvara to the HE1000v2. It's not going to win design awards, but to me it has a much, more sleek, modern styling than the Abyss. I just don't find the Abyss Phi style very attractive at all. It reminds me of the very outdated Affliction brand of T-shirts and looks like a set of cans - a hard core gamer would buy to play Call of Duty or whatever the latest First Person Shooter is.
As for Stax - the only thing that bothers me about going to that system would require an electrostatic amp - maybe its just perception - but I feel like I would not have many options to swap components. The counter argument of course - is that Susvara is so power hungry, your choices would be just as limited, but whatever amp I choose - I could also use them to mess with all the other non-electrostatic headphones in my collection.
Let's talk price. Price $6000 is ridiculous. But this is the hobby we've chosen to get into. I already think spend $150 is ridiculous, yet I own like 15 sets of headphones and Focal Clears which costed $1500. I have a DAC/AMP on order that was $2500. Just stupid. - I've long past what should be reasonable to pay for a headphone, so I will save my pennies to try and get a Susvara in the near future. Of course I wish/hope it drops in price.
I have always relied heavily on research and other users opinions when shortlisting audio gear. From my own listening experience, I found that I really don't feel the same about audio products that others in the community have raved about or hated on.
I think you really do have to listen for yourself and form your own opinion. The REALLY good stuff will stand out on its own. It will create an experience you can't forget and crave for. Susvara was one of those for me. My car stereo sounds like crap now - and all my other headphones aren't good enough anymore, when I once thought they would be all I'd every need.