I owned the HEKse for about 7 months and upgraded to Susvara which are my true endgame until I get an HE1 lol!
Here's my ranking of top tier headphones I've heard or owned as with an added tonality summary. Owned is
bolded:
HE1: "Real" and holographic like nothing out there. One single coherent blanket of cohesive sound/ nothing in your head.
Susvara: Near perfect tonally/ ever so slightly bright with ever so slightly too fast bass
Shangri-La Prototype: Ethereal, speaker like, but brighter and less convincing tonality compared to the two above.
HD800: Natural sound, great bass after EQ, tamed highs but still have dynamic and attack (I use Oratory1990's Harman Target curve, and add a bit more bass boost to his shelf up to 100hz. I will never ever listen to a stock HD800 again, it's poor.) HD800 is legitimate. I sold these in favor of a Focal Clear 3 years ago because I never dared change their tuning as an anti-EQ person. Turns out I got around to EQ'ing these and 100% vouch for it. They outshine Susvara sometimes even!
HEKse: Neutral/Bright. Trickle down of Susvara, more stage height and width (diffuse) lacks the same quality bass and especially grainier treble. Still my choice for end game performance and gear flexibility for price. Needs treble smoothing. I feel like HiFiMAN wanted to makes an HD800-like phone but with punchier, cleaner and more textured bass. Sadly treble is grainier than HD800.
Utopia: Neutral/bright. Sounds super focused and coherent, dynamics for days, transparent, punchy with amazing holography and proportionate staging in all axis'. Sadly stage width isn't as wide as competitors, but is more coherent than most regardless. Metallic timbre sometimes even on a warm system. I'd call this the best end-game for a single headphone user, paired up with a nice tube amp like Cayin HA-300A for example.
HE6 4 Screw (early production): Natural/aggressive. Some of the best and most authoritative bass and treble in a planar, much more grain-free up high vs all HiFiMAN's besides Susvara. More open and diffuse than HE6 6 screw, cleaner bass and image. Sounds more like a dynamic or e-stat. Importance of a powerful amp can't be understated.
SR007MKI: Neutral/smooth: Not an e-stat guy at all because they have no tactility in bass, but these are the sweetest and most natural stax I've heard.
SR009(S): Neutral/bright and neutral/bright w/ bass boost. Impressive with great recordings, detail monsters. Great imaging. Heard with KGSSHV and the portable Stax amp lol. Has no soul, has no tactility and visceral impact. Incredible with great recordings.
HE6 6 Screw: Natural/aggressive. Punchier bass and edgier treble vs 4 screw. Much easier to drive, more focused image with better depth projection. Really in your face and fun headphone, treble is unpolished and sometimes too metallic. Scales with powerful amps, again.
LCD4: Natural/dark. These have some of the best staging in sub 5k headphones. Very open in all 3 axis, nearly as wide and high as HD800 which caught me off guard. Not my preferred tonality, but it's done fantastically and allows for musical enjoyment with almost any music... provided you stick to this single headphone and calibrate to it in a listening session. Phenomenal bass, a bit too lingering imho, but the best after Susvara, outperforming HE6 except in visceral slam.
HEKv2: Natural/holographic. I think the tuning of this headphone is amazing. It sounds analog, music sounds "real", barely ever glare-y or digital, despite a peaky region. Issue with this generation of Hifiman is that it's a bit too soft and lacking tightness and dynamics. Bass is more bloomy than tight. HEKse remedies to that, but sacrifices the stage width and more natural timbre of HEKv2 in favor of the more focused and punchy attack.
K1000 Bass Heavy: Neutral. Most "neutral" headphone I've ever heard. Helps that the bass rolls off super early lol. But these, like the LCD4, sound incredible if you have a listening session with just it. Resolution and transparency is barely any better than my HD580 Jubilee, but the staging is addictive and satisfying with the right type of music, and tonality is near perfect with music that doesn't have a lot of low bass. It still handles bass superbly until 90hz, it's just not visceral. Can be fun with a subwoofer, but requires careful calibration and always sounds slower with a sub.
The rest:
Arya, Empyrean,
Clear, LCD3, HD580J, HD600, HE500,Sundara,
HD650, etc
. Not elaborating as I'm tired of writing. I can give my take on them if you guys care/ ask me
My rig is Singxer SU-1->Holo Spring KTE->Rebuilt and modernised McIntosh MC225. Chain sounds natural/neutral with neutral bass, and lots of airiness and no digital glare (tonal smoothing of R2R DAC).