What is the best sound system you ever heard?

Here is a system I heard at a friend's house in 1978: Thorens TD125/Rabco SL8/Panasonic Strain Gauge cartridge, Marantz 7 preamp (used as a line stage), pair of Futterman H3AA OTL amps and a pair of Quad 57's. After hearing this I resolved to get a similar system!

Complete MBL system.  Radialstrahler 101, 9011 amp, 6010 pre-amp, VPI Aries. 

The Infinity IRS V speakers with $100,000 of associated PS Audio gear at PS Audio is a strong candidate for the best system I’ve ever heard. 

The one way up on Red Mountain Aspen CO, the one Dave Brubeck used for practice late 60s early 70s. All McIntosh everything. Some unknown monster midrange horn, time delay system, and concert grand piano of course. Also some kind of Joshua Light Show panels. I recall there was a big bunch of Ducati racing motorcycles in the garage.

Alchemist The Pre & The Mono (x 2) amplification, Alchemist Forseti CD transport & DAC, Nottingham Analogue Mentor turntable, Ruark Excalibur speakers.

That was 20 or so years ago of course, so how it would sound today I don’t know. Still, nothing I’ve heard since has come close to making the same impression.

A few other stand out impressions are:

KEF Reference 207 / Karan Acoustics KA I 180.

B&W Nautilus / Electrocompaniet Nemo mono blocks.

Avantgarde Acoustics Trio / EAR V12