As you know, I recently got HE-6 and have an A-100 Emotive on the way. That is a budget friendly way to get massive power to them, I'll see how it goes vs my other setups (which are great).
The Jotenheim in balanced mode with the HE-6 is amazing, period. But everyone says speaker amp and mega watts of headroom for the HE-6. I can imagine they have unlocked potential, they are just insane sounding headphones. They are the best headphone I have ever heard, hands down, (probably yours too?) and that's without any speaker amp driving them.
From what I understand the newer Hifiman headphones don't go all out for that thrilling, viseral, adrenaline pumping sound the HE-6 is so well known for... at least from what I've read the X, HE-1000, 560, etc don't have that aggressive powerful attack of the HE-6, which is what I love most in a headphone. I want a headphone to make my jaw drop!
From reading it doesn't seem Sundara or Ananda really have that aggressive characteristic in spades either. I don't know, I haven't heard all these so I can't say with a degree of accuracy. They are probably amazing in other areas but I don't know if you are looking for a headphone that attacks you with sound, if there is better than the 6.
The reason is I listen to a lot of EDM and Electonic music where you really want that fast and aggressive attack. But then switch them to vocal tracks, and their clarity and nuanced resolve is stunning.
I could imagine it would be hard to find someone who's heard all these as the Ananda's are so new and the 6's are getting harder to find nowadays.