(1) Dealers can only carry certain brands, and the arena of choice in high-end is far too wide to even consider presenting anything more than a restricted sample available. That kills it right there ...full stop.
(2) "Best sound" is purely a highly deeply biased and purely anecdotal value judgement that is bespoke unique to an individuals whims and bias with no benchmark for comparison or assessment. That kills it again....full stop.
(3) An "obligation" is a course of action that someone is required to take, whether legal or moral. Without drowning in the impossible swamp of generally debating the former, even the latter is governed by the afore highlighted caveat emptor guideline. The latter does not seqway into the former with the possible exception of an unlikely legal protection statute transgression for being misleading or fraudulent, that is not the context of this thread nor even remotely existent in high-end audio where the debatable and conflicting differences in sonic signature are just a flavour of the month.
Time to kill off and mercifully bury this thread and let's move on.