Does It have to be loud?

It is great advantage if you only need 70 dB. It greatly reduces the cost of a system. Unfortunately it only leaves you with 80dB peaks less 30dB noise floor = 50 dB dynamic range but it does offer an advantage in that almost any system will do a pretty good job at these modest levels including Bose speakers. No need for market leading 120dB THD+N performance as it won’t be audible anyway.

I listen at 50 to 60dB measured at listening chair.

When I play Nirvana, I can listen to it at 50-60 db outside my building.

No and you can save a lot of money that way.   Wear and tear on your ears as well if you keep it below 85 db or so most of the time.  No good ears, no good sound....

It’s producing large quantities of good sound that is hardest and most expensive.

As amazing and sensitive our sense of hearing is, it is insensitive to certain aspects of music at low volumes.
1. Dynamic range - when you listen at low volumes, loud passages aren't loud
2. Frequency extremes - our ears can't' hear deep bass frequencies or extended high frequencies at low volumes very well. 
3. Harmonic overtones - harmonics, and the "feel" of the space of where the music was performed is lost at low volumes. 
This is why music is played loud at shows and for demo purposes. Although I agree that most tines the "demoer" overdoes it.   

Several good comments above that deserve amplification.  I dont know what the SPLs are at my chair but i do know that:

1. the ear has a reduced sensitivity to extremes at low levels, so too low is not ideal
2. Noise will mask low level detail if the level is set too low.
3. Music also provides "feel" - does the kettle drum vibrate you?  That's realistic.

Too loud certainly overloads both my comfort and my room( and generally not my amps, which i have the ability to measure, roughly).  But too low obscures detail, even things like the texture of vocals. You may question if its a "good thing" but at moderately hgih levels i can often hear the artifacts of mixing.  not so at lower levels.

And gladly, despite many decades, many concerts and tons of listening, i still hear very high frequencies in my lab - 15-20k. Down in audibility, yes, but I hear them. When i'd travel to our NY lab decades ago, my dog used to get annoyed when [name withheld) turned his oscillator up to a HF rather than off :-)  Cant fool the dog.