I have one recording that I've always used, regardless of the speaker...Pink Floyd's ~ "Wish you were here", Title track. David Gilmour should sound like he is on a 3 foot stool, dead center. You should hear his fret work on the left side move from the left back to almost center like a real guitar.
I'm not a musician but, I've heard enough live acoustic guitar to know what it should sound like. You can get the remastered 2011 Parlophone CD dirt cheap on-line, it's a stunner on the Summits.
You should also pay attention to the footers, the tilt of the panel is very room dependent, it's not like the Italians style of driving as they rip off the rear view mirror..."What is behind me is Not important", HeHe!