The sound science forum here reminds me of the flux capacitator.
Voltage and current. That is what is proper.
Enthusiadt level means that those are sufficent, everything is matched(impedence etc) but then using better parts, practices, circuit layouts etc for above regular.
Truly what something is said or regarded to be; genuine: "a proper meal".
Satisfactorily or correctly: "my eyes were all blurry and I couldn't see proper".
The word was used as an adverb. Which suits our conditions.
If it was used as an adjective. It would leave more wiggle room as it is what is more known by the crowd base to be