My grandfather's JBL Paragon (from about 1959/60/61). I didn't sell it; my grandmother did after he died in 1978. It didn't sit well with her idea of living room decor. It may have overpowered the room visually; but sonically, it was superb in its time. Don't know how it would fare today.
You are invited on a "trip down memory lane".
This thread is, of course, mainly hyperbole (or less kindly B.S.). But that said, what is an item from your sound system over the course of your journey that you would most want to have back? I have sold some that I, likely, should not have. Mine would be the CJ ART pre-amp and the Magnepan MG-20....a distant 3rd and mostly nostalgia would be the Dahlquist DQ-10 speakers.