EQ is the one thing that I've found makes truly "night and day" differences on a single headphone. I'm also glad you tweaked the EQ preset to your liking.

I once compared my EQed KSC75 to my EQed SR-L700mk2, and the Koss was really good. I did not expect it to be that good vs the Stax, because the stock KSC75 is difficult for me to listen to thanks to some sort of ringing at around 5K (ringing as in I hear something similar to microphone feedback at the trailing ends of some tones in that region). That went away with EQ and resulted in a very open and capable sound from a $15 pair of earphones.

That knowledge and experience did not prevent me from buying an even more expensive headphone later, so there's probably no hope for me anyways. But yeah, EQ is great!