Audiophile's are famous for spending a lot of money on "snake oil" to get results that objectively cannot be heard and then claim the sound is better. Sometimes the sound is better, but the human ear cannot tell (lab equipment can). Of even the best lab equipment cannot find a difference.

Good enough if you are happy is good enough. Maybe you can do better in ways you can hear, but with "Flac is my source, decent DAC, decent cans" you are probably getting close to the edge of what the human ear can hear anyway (assuming good audio in that Flac, and the DAC/cans really are decent as you claim)