IIRC, I got the UCSD Pascal system up and running on it in my senior year of college then donated it to a high school. Probably with a (non-Super-)Serial Card and a Disk ][.
Later, I owned a //e for a while, as well as couple of IIgs systems. I had a KIM-1 for a while. There used to be "junk" warehouses around here where such things could be found for $20-$30 - but they've all shut down, I think.
I have no 6502/6516 systems any longer. Mostly for lack of a workshop in which to store and use them all.
I think my most retro computer now is a Tandy PC-6 pocket computer. I keep telling myself I'll wire something to its parallel port and have it do some chore for me, blink some lights, count raindrops.. as a conversation piece.