When is your Hifi good enough?

Willie that sounds like me too. 

When the speakers disappear and I get goosebumps. Joe 

When my focus for improving sound redirects from gear to acoustic room treatment.

Obsession has no limits, so the answer is obvious whether it is audio or anything else.
It is all pornography, in a manner of speaking.

A system is good enough for me (as for others who have said the same here and elsewhere) when I find myself completely absorbed, consumed, and inhabited by the music---becoming one with it, rather than thinking about the sound of it. Good equipment, and even good sound, is only the means to an end---more appreciation and enjoyment of, and deeper connection with, music---God's greatest gift to mankind (followed closely by dogs ;-).