Amps, pre-amps, and DACs all improve at different rates vs cost - so you eant to update one snd must buy more. Then the liklihood that all of your components are of equal quality to start with - a statement of faith/ belief.
I hated every CD player and DAC i heard for years except two 20k players from Krell and ARC around Y2K - until the two high end multi bit DACs from Schiit 15 years later. DACs are not all alike.
My vote: used BHC and used HD-600 (buy new pads).
Not even a Rag, v281, or Bryston BHA-1 can drive the 600 anywhere near as well as an OTL. Much better soundstage, bass doesnt roll off until 55 Hz not 75 Hz as with SS amps. Also that mid treble that gives a slight scouring pad edge is gone. No need for EQ although you can tease some 35 Hz out it.
Not perfect but, if its all u listen too and you dont need low bass like an Abyss or LCD-2 - the musicality will blow ur mind. For maybe under $600.