Hello Jeremy
How to set a good EQ setting in audiophile = a professional + a subjective issue. Sometime we hire a professional to set the EQ for our equalizer amp for our listening room.
Luckily, Apple has already setup few choices for the user to select. I choose "Treble Booster" as it fit my listening room which is covered by floor carpet and with some sound absorber. I agree at the normal envoirnment, the EQ should be set at flat.
Last but not least, there is no a such golden EQ setting, you should set a setting which fit your preference, the most important is to enjoy the music listening