I have tried several headphones in that range (HD599, HD58x, HD6xx, HD560s, SHP9500/9600, Fidelio X2HR, PC38x, G4ME ONE, AKG K712 Pro) some of them I used exclusively for months like the SHP9600, HD6xx and HD58x.
Somehow I still find the HD599 SE to be the most enjoyable headphones in this category. They’re like the perfect balance of fun, detail, soundstage and clarity. They’re not too fun like the X2HR, not too detailed, but just perfect for me. I compared them against the HD560s and honestly the 560s were almost my least favorite headphones but I’d choose them over SHP9500 and the gaming headsets (PC38x and G4ME ONE). The HD560s had more clarity but the soundstage was noticeably narrower than the HD599 SE and I think they had no slam to them or fun factor. They’re like HD6xx but slightly worse and barely have a wide soundstage but that’s just my casual opinion. I know they’re quite loved headphones. I don’t know how but the HD599’s have magic to them lol or I’m brainwashed at this point.
I don’t know, those are pretty audiophilish takes that match up with the signatures and characteristics of those headphones. The 599 is a V-shape headphone or “fun” headphone at its core and it’s not necessarily as appealing to neutral listening type hobbyists who gravitate toward open backs. It’s still a really good pair of headphones, there’s a lot to like about them.
If you take the measurements and attributes of the 600 and the 599, go through them comparing one by one, there is not $200+ worth of differences there. There’s some metrics it’s better in. They are both very proficient headphones at what they’re designed to do.
Just another reason why the hivemind opinions on headphones aren’t always going to match up with a person’s listening preferences. It’s a great starting point but trusting then verifying is a good audio practice. There’s no headphone I’d want to listen to less than a Beyerdynamic and plenty of people absolutely love them. I would rather listen to the Sundaras over every other Hifiman headphone excluding the Susvara which I haven’t heard. Having contrary takes is a good thing in audio, it means you’re listening with your ears and not the influence of others which is an easy trap to fall into.
My most listened to headphone at present time is the Fostex TH-600. I know what it measures like. I know it’s a dated type that’s been eclipsed twice over. That’s just what I want to hear right now. I’ll circle back and go through my neutral listening cans when I’m tired of them.