ADS 200s: Historically, these little "studio monitors" represent the first legitimate mobile audio (car stereo) system ever assembled. They broke the "sound barrier" and took us from Clarion coaxials (yuk!) to true high fidelity in a car/truck/van. We built competitive car audio systems for years (including winning a national championship trophy) and these have a special place in my heart. And, in my current office system. Low end is handled by custom-built (teeny tiny) passive sub to integrate seamlessly.
Nakamichi TA4: These were introduced around the Golden Age of "big boy" receivers and featured Nelson Pass designed Status technology. In my view, they were head and shoulders above what was offered in the day, and sound quality was more akin to a competant integrated. When we upgraded a system of a previous TA4 customer to high(er) end gear, we boxed up this receiver for him and placed it in storage in his basement. For years, I begged him to let it go and, finally, he was willing to part with it. It is currently boxed up and sitting in my loft (with plenty of other stuff), not being used. This topic reminded me that I need to get it out and "exercise" it a bit, and do a little checkup and maintenance.
Klipschorn 1958: Got this in a trade from a customer who wanted a pair of current high quality bookshelf speakers. The drivers are correct and the speaker sounds pretty amazing for its age. Not sure how/if I'll ever use it. But, have no plans to let it go.