There's good audiophile investments like what you listed, quality headphones or a good set of bookshelf speakers, or hunting down a quality FLAC rip of the 2012 vinyl only remaster of the 1997 Iggy Pop remix of the original 1973 David Bowie mix of Raw Power, and then there's the stuff the reddit fanboys go after like getting super premium deoxodized copper cables or whatever. Cheap copper wire from home depot or a wire coat hanger yet these nerds refuse to believe it's the case because of their sunken cost fallacy.

I spent most of my teenage and young adult years listening to a Clip+ MP3 player loaded with punk music recorded in a basement somewhere, good headphones was all I needed to get the full effect of how bad the recording is and I won't have it any other way.