My feeling about the stock LEAF audio system is that is has a peak in the treble region. Just going into the settings menu an taking the treble down a notch or two makes it better, IMHO.
I had my interior wrapped in leather and when they had the door panels off, I unscrewed the speakers and put some leftover sound deadening behind the speakers (on the door) and then put the speakers back in. Much better sound as well.