Yes a tube buffer for whatever, SS or tube amp. Although SS would make more sense. It does have volume control.
About end game, I don't know. One would have thought Audez'e was end game but I didn't stop there. YMMV of course
right now am planning to make shure srh 1840 with a competent $500 SS like fostex hp a4 or a dap like ibasso dx90 as end game.
this much I can reasonably spend and wont go far enough into diminishing returns territory.
a cheap tube amp as side setup would be nice, down the road.
have not heard audeze. I have heard they make very good first impression. but in long run people tend to sell them. of course take this as pinch of salt as this is not personal experience.