Sound quality is largely subjective. Well I mean I guess those of us that "know better" know what sounds good from what doesn't but when it comes to source material I think you have to choose your own.

Someone could tell you to test out SQ with classical music for example but what good would that do you if you never listen to classical music? Most modern popular music has it's dynamic range compressed to hell unfortunately, so it can't really be considered the best thing to test out SQ with, but if it's all you listen to for example, I don't see the point in setting things up for music you don't listen to.

Unless you're competing and trying to please SQ judges I would stick to what you'd be listening to on a daily basis.