Headphones, and especially IEMs have reached a level of maturity where the only audible difference between most >$20 sets is the frequency response, which can be equalized with parametric EQ.
Ditto for most DACs and amps, unless the noise floor is audible and / or they don't drive the headphones loud enough.
Cables don't do squat.
The secret to the superiority of vinyl albums lies in the fact that they're not compressed to death like most digital recordings.
Tube warmth is 2nd order harmonic distortion that can now be completely done in software.
A healthy dose of digital signal processing (parametric EQ, de-essing "poor quality" recordings, HRTF processing to improve spatialization) can do more for the sound quality than $10000 on equipment.
Edited by Joe Bloggs - 2/26/13 at 5:39am