What is the best sound system you ever heard?

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

In recent memory it has to the Kerr Acoustic K320 speakers. Nothing spectacular, but nothing obviously wrong - no sibilance, no bleaching, no cabinet issues. Eminently listenable fuss free sound through a Pioneer CD and smartphone streaming no matter what they were asked to play. Not sure about the amp, but it was a large black box with handles on the front.

I should also mention being stunned by the spooky imaging and scary dynamics of the Avantgarde Trios some 15 years ago. System featured a (ridiculously) deep plattered turntable with a, wait for it, £5k cartridge! Amps were some exotic valve types.

It was almost a time machine experience, but the trouble was the young chap demonstrating only played some 1950’s Jazz and didn’t seem keen on trying anything else. I still recall him telling us that it cost £5 in stylus wear every time he played a record.

Having heard systems of price ranges going well into 6 figures, got to say it's still a remote facsimile of live. Moving beyond that, I think my system is pretty excellent. 

Nothing is more absurd than to compare recorded music to live, yet people do it all the time.

Easy for me to answer; this Magico/Solution system I described a few years back:

https://forum.audiogon.com/discussions/2c-hifi-epiphany-worlds-best-system

Nothing has come remotely close for me. Returning to the realms of reality, this is my current 2C analog/digital system that sounds and looks fantastic to me:

https://systems.audiogon.com/systems/7324