Well we never know but I think that the headphone stack is probbaly close to endgame :
Amp : Cayin HA-1A Mk2 (endgame)
DAC : Cayin iDac-6 Mk2 (endgame)
"Streamer" : Cayin iDap-6 + iPhone (probbaly endgame, i do not see other sources)
Heaphones : Sennheiser HD560S (well I am 30 so I will probably purchase at least another model, but it will be out of curiosity/vanity since the sound produced by this stack is perfect to me --> endgame to my ears, but probably not the last purchase)
My full-size hifi is not endgame at all however.