I can understand, as you can see they dont make the successor or update of those AD2000x, this i believed that's 2012 product, hd660s now even comes with V2 revision, hifiman update their line up too with their revisions, audeze also did the same, they can update with detachable feature or updated headband or something but they choose not to, why i wondering ?! Do they update their packaging as well or with the new cable or something ?! Take look at sennheiser they have relic product like Senn HD600/650 they choose to update those, with new packaging, new accessories, AFAIK there's no update for AD2000x yet.
They made ADX5000 in 2018 for sure but that's in different price range area.. and set to be compete with hd800 arya line up, they choose not to update or renew AD2000x for some reason.