"Better" can be one of two things, depending on the system-builder's goal:
Better is a component that makes (lets) a sound system sound more pleasing to that person; without a specific reference in mind, other than that person's sonic preferences. Or:
Better is a component that makes (lets) a sound system sound more like what live music sounds like. Familiarity with the sound of the real thing makes it possible to have this be a useful reference, in spite of all the variables.
Better is a component that makes (lets) a sound system sound more pleasing to that person; without a specific reference in mind, other than that person's sonic preferences. Or:
Better is a component that makes (lets) a sound system sound more like what live music sounds like. Familiarity with the sound of the real thing makes it possible to have this be a useful reference, in spite of all the variables.