When your system starts to tell you how the engineer positioned the mikes and what kind of mix he applied to the feed, you know you're getting there with refining your system.
Listening to classical piano music a lot, I notice this constantly. What perspective did the engineer choose. To the side, to the front or the back. Are the treble and bass ends of the keyboard panned to left and right speakers, or blended. How distant is the piano. Etc. etc.