Low cost amp and dac... Schiit BiFrost and Asgard 2 or Lyr.
On the idea that people shouldn't roll amps or dacs to tune a headphone and instead just buy the right headphone... wouldn't that be nice. Top shelf headphones can be counted on one hand. And they are wildly different. If you like the HD800 but wish it had a bit more fullness, changing to the fuller LCD-3 would only result in landing in a place where things are overly full, resolution has been decimated and staging is all but non existent. And vice versa, an LCD-3 owner wanting a touch more resolution or more treble presence would find the HD800 completely top tilted lacking any lacking that thick liquid sound they like. There just aren't enough options to tune at the headphone level. Probably why a butt ton of headphone users like tubes. You can swing a headphone drastically with tube swaps that act like an EQ without messing with phase or bit resolution.