Does It have to be loud?

@gdhal - I agree that each recording seems to have a level, given room, system and recording, where everything comes together.
I think that sometimes, "turning it up" is meant to get more immediacy, impact and get the system out of the way, and if everything (including the recording) isn’t up to snuff, it’s just playing louder at you, but doesn’t sound more real. So I get @geoffkait ’s point, in that some recordings are compressed where there is no real dynamic range- a/k/a loudness wars.

I went to hear Crimson several months ago in a good hall here in Austin. The next morning, I played some material from the 2016 Live in Toronto LPs- there was just no way I could reproduce the scale of that recording, or the level of bass, in my room (which is fairly large by normal residential standards) at anywhere near what I heard live. Nonetheless,the recording and system acquitted themselves pretty well in that half-assed live v. recorded comparison.
I’ve aimed to get the resolving power of my system to a point where it doesn’t have to be super loud to be fully engaging and I do listen to a lot of very hard rock (mostly early stuff, before the term "proto-metal" was invented).
It is a shame that some of the records I like from that era, e.g. the first two Zep albums are not very good recordings. But, there are some that are- try Brian Davison’s Every Which Way (U.S. Mercury) circa 1970 or 71. You can turn it up and enjoy it like you would a well recorded jazz record- sounds like early Traffic. Some of the better known heavy rock records, like the first Sabbath album on Vertigo Swirl (UK) sound very good, even though they are primitive.
I find that I have to wear ear protection at almost all live rock events. They are just too loud and too often, overwhelm the room.

Personally when you start going over 90db  not only are you abusing your hearing 
But permanent hearing loss + tinnitus. Also room  reflections,  your room and  
Natural flowing  music will be an after thought ,unless you
Have room correction of some type.

I like to listen at the level I imagine the music would be played at if it were a live performance. I’m listening to John Fahey play acoustic guitar right now (with a pickup and amp, it sounds like, on his record of hymns, "Yes! Jesus Loves Me"), and after reading this got out my SPL meter and read about 80 dB on the loud parts.

I like orchestral music to be loud in the loud when it should be, of course. Of course there’s a lot of dynamic range in orchestral music. I wonder what concert hall SPLs are like.

A lot of the 50s and 60s-era acoustic jazz I like doesn’t need to be very loud to be enjoyable because it’s not too difficult to distinguish among four or five instruments.

Now I’m curious and will test myself and the music to see what works.

What’s being measured, average SPL or peaks? And how measured, e.g., test tone, music?

Just put on "The Dave Brubeck Quartet in Europe," and Brubeck's big piano chords are peaking at 80-83 dB, and the applause at the end of each track is irritatingly loud at 85 db. It seems I need the volume up a bit to hear the bass, although that might be a deficiency of my system or (rather small 12.5' x 15') listening room.