A moment when you realized better sound was possible.

Back in the late 80s I was able to pick up a Luxman turntable with a decent MM cartridge. Several years later I was helping in the construction phase of a recording studio, where payment at one phase in the overall effort was in the form of used vintage audio gear. Not knowing anything of the company or quality of equipment they produce, I chose a McIntosh C20 tube preamp for that paycheck. A few years later (late 90s) I was able to pick up a pair of Proac Studio 1s (again, not knowing anything about their reputation). 

At some point thereafter I put them all together with record play of John Lennon's 'Watching the Wheels' and, for the first time in my life, experienced a sound stage (i.e. sound imaging). I've been chasing the dream ever since that amazing experience...

Current state = that same Luxman TT, a Luxman CL-38uSE preamp, Atma-Sphere M60 OTL amps, and those same Proac Studio 1s.

Freshman year of college I heard some DIY speakers some upperclassmen in my dorm had made. Eventually I got to visit a music lab where they had made a pair of subs with 24” drivers. The cabinets were multiple layers of of plywood with sand between the inner and outer box. I think the main dimensions were 8’hx4’wx12’d, but I’m not 100% sure on the depth. I do know they had left the outside as full sheets to simplify the cuts and there was a long heat sink extending from each driver’s voice coil. No idea what the upper range speakers or amplification were, but I’m sure it was massive. I remember one specific test track vividly. It was an outside setting with birdsong, the wind rustling long grass, and a small stream that had lifelike realism. Then way off in the distance was a barely audible whine that slowly grew in volume until it became recognizable as a plane. The plane gets closer and the volume grows until you could literally feel the jetliner flying over your head as it came in for a landing somewhere beyond the speakers. It was surreal. 

Likely to get flamed on this one, but my first "system" as an early teen was based on some no name floor speakers, a Technics integrated from a rack system, double cassette deck, and basic Kenwood TT.  Loved it.  Crushed the heck out of some cassette listening and raided my older sisters' LP collections (AC/DC, Billy Squier, Foreigner, Kiss).

Got an off-brand CD player from a pawn shop, first CD haul was Tom Petty, Billy Joel, BTO.  Hit the play button on that thing, and was blown away.  Not trying to argue that CD is better than tape or vinyl, but on that system with those components it sure as hell was.

I have still been living in mid to upper midfi, but heck I am happy with the way it's going.  With some of the high value proposition components out there these days, starting to feel like I am putting together a legit experience.

iron47 -- You're on your way!  Just try not to go bankrupt too quickly. And try not to make your neighbors too murderous.

Thanks @edcyn!