> 24-bit audio is obviously a noticeable improvement even on $150 headphones
Not going to question your subjective experience, but I do not think most people will hear any difference between 16 and 24 bit playbacks under normal conditions, even with fancy headphones.
"120dB is greater than the difference between a mosquito somewhere in the same room and a jackhammer a foot away.... or the difference between a deserted 'soundproof' room and a sound loud enough to cause hearing damage in seconds.
16 bits is enough to store all we can hear, and will be enough forever." [1]