That Strads sound is some real sound reference point I d say!
Yet not many people will be able to identify that a Stradivarius is being played in a recording (though they may prefer it's sound when comparing it with another recording), and those who do, probably don't need a high end audio system to do so. Morricab in fact posted video recordings of his ex (if I remember correctly) playing different violins, and the differences are pretty obvious just listening with a phone.
If a good system can't allow you to differentiate the sound of different instruments (and the musicians playing them) - even if you cannot name them - then you need to find another hobby.
I am no expert, but I can instantly recognize Johnny Hodges playing saxophone, for example, as many afficionados will (there are no super-powers involved). Does that give me any authority in terms of audio? No. By the way, I can do that listening on my phone...
Differentiation is one thing, but what about how accurately a system and recording reproduces the sound of a given instrument? Here again, I assume most people will be able to tell the difference between a violin and a cello, but very few will correctly identify which violin is being played. Assuming someone was intimately familiar with the sound of a Stradivarius, would that be helpful in assessing the accuracy of a recording and system? Perhaps, but for all of us who are not, you can simply record your voice (or even better, someone's voice that you are familiar with) with a good microphone and compare how it sounds on different systems. Results may be surprising...
All this to say that "natural sound" as a reference is completely meaningless unless you get very specific and use a performance and recording that you are very familiar with (you have actually heard live, and can perhaps even hear live repeatedly). I doubt that many here have done this.