The systems I like are not fussy in that they sound good with a wide range of music and with all sorts of upstream electronics. However, that is not to say that one cannot hear the difference when components are swapped out. I have sat through tuning sessions where small changes are made such as changes between internal wiring choices, and with great systems, such changes can be heard. But, they are not fussy in that changes and improvements can be heard, but nothing sounds bad--just different.
What I like about custom systems is that the sound of the speaker can be changed to suit the customer's preference. I have observed changes--to internal wiring, choice of drivers, choice of capacitors, amount and type of sound absorbing filler--being employed to get to the sound that the prospective buyer wants.