op
your findings are bizarre Ess chips are considered very transparent however the Ess dacs you tried wer not using their highest performing dacs which are the 9038pro series
theES9038Q2M is an older and less capable chip which doesn't represent the best Ess does the older dac is a two channel dac the 9038 pro has eight channels most companies employ all eight channels to lower distortion with the 9038 pro
by the way many of the worlds best dacs use the 9038pro: lumin ideon weiss all use this chip and all of these companies products are considered superb
one could also wonder how you are feeding your dac?
most of these dacs sound best playing high res via USB and not through spdif the source feeding the dac is also extremely important.
if you want transparency look at chord.
Dave and Troy
audio intellect NJ
digital specialists