Well… it won’t matter once you listen to music on them with your shitty 20 USD headphones.

Yea, I have found by far the biggest effect for me (and I have to imagine most people) is the speakers / headphones, not the digital processing or even the audio converters.

headphones or speakers can’t add the detail that mp3 (or streaming in whatever format) eliminates. Compare a CD and mp3 of the sane track with a decent headphone (or a speaker) and you will hear that compression changes sounds.

but it all depends on what kind of music you listen to

My point is just that most headphones that are cheap can’t reproduce MP3 quality, so until you get good enough headphones to hear the difference, getting a FLAC of the same song isn’t going to really be noticable.