Years ago I bought a Mac C 22 and whatever was the lowest power amp Mac made at same time at an estate sale in the early 90s. They came with all their literature including the David Dean Smith reciepts. I had three offers on the equipment by the time I made it out of the house. But I was in New Haven too late for the actual store -- I think it closed weeks before I moved there in 1979.
My memories of stores include Tech HiFi in Bryn Mawr PA and the Sam Goodies in Ardmore PA, both surprisingly good stores where I spent lots of time, and then also the wonderful Soundex also in Ardmore, just down the block from Sam Goodies, where they had Quad tube equipment in the window and Voigt Corner horns, Thorens TD 124s and Janszen/AR combos -- my enthusiasm for vintage equipment is a result of going there. Barclay's further down the Main Line was also fun -- Transcriptors, RTRs and so on. Soundex is still in business and full to the brim of old stuff. But most of their business is repairs, and, if the reviews posted on the net are an indication, they may be off their game.
Audio was a lot more fun back in the early 70s.
Incidentally -- does anyone have a copy of Audio Alternative by Marc Toback (if memory serves) -- a coffee table book about vintage equipment that went in and out of print in the mid 70s?