I bought some stereo speakers a while back. The store only sells what's on the shelves, nothing boxed in the back. When I asked the guy about this he told me "the advantage is they've already been broken in to some extent" which I thought was a crock but can see now it wasn't. Thought I had noticed some difference on the high end, on some high soprano/alto vocal parts it used to have a ringy kind of quality on some higher frequencies that don't seem to be there now. I've been playing them for about 4 months now and there seems to be an improvement in overall sound, but especially in the higher tones/overtones.