I got interested in quad in the early 70s, and although I’ve had lapses in my ability to play my vinyl quads, I never lost interest in being in the middle of the music. I started off with an SQ decoder because the format required a minimal change to my existing “prety good” stereo setup. I didn’t get CD-4 because it would pretty much require replacing the heart of the system, although I played a few QS records through my SQ decoder, and it was usually pretty groovy sounding (still into groovinesss after all these years).
My lapses are mostly due to the size of my vinyl collection being moved to new homes where I needed shelving (see my avatar from the house before the one I’m in nowj. Today, my vinyl is packed up in boxes, although my digital collection is available. I have decoders for SQ, QS, and CD-4, and as a retired electronics design engineer, I have a future project to build multi-channel audio to HDMI encoders so I can integrate them into my home theater. But first, the supply chain needs to get my Grass under-drawer slides into Idaho so I can get the shelves built. Looks like next year, but who knows?