DQ10s for sure were the first 'moment'.
Magnepans in another college dorm room a couple years later.
I will never forget the 'he is in the room singing' feeling from hearing Frank Sinatra on vinyl in Honolulu 1990. It was at a high end shop on great bookshelf speakers via a turntable and electronics (all quality but names forgotten).
That moment really showed me for the first time how magical music could sound if portrayed superbly. It convinced me to upgrade everything and the disease started...