If the amp is left as is (without installing this resistor), I am assuming that I am not realizing the full potential of the SEX amp, correct?
This was the initial thought, as the headphones present a pretty light load at the outputs, although it appears to make very little to no noticeable/measurable difference in the SEX amp.
Normal installation of these resistors was to use the speaker binding posts to secure them, but I wouldn't even bother using them.