What decibel level do you listen at? What is ideal?

Pass x-250.8, Bricasti M1se with network card, specialty Tekton Encores,( all 175lbs each)  30'x60' 16' ceilings shop, dual SVS SB4000 subs (listening area 1/3 of that, speakers 12' apart 15' away, stream qobus via Audirvana  Rock and roll only, mid 80's to low 90's ( due to speakers efficiency, all done within class A of AMP) Metallica, Pink Floyd, Led Zeppelin, Lynyrd Skynyrd etc. 72 YOA, still with pretty good hearing!  Also Project RS2T with linear power supply.  YOU ARE THERE! closer than you think after a Buffalo Trace or 2. Robert  TN   A shout out to you all for your help and assistance over the years,  Thank you, and Audiogon forum

Depends on music, mood and environment (sleeping spouse, guests, etc.)

To me, every song has its optimal volume setting.  I rarely listen above 90dB.  OSHA protocols state that risk of hearing loss is minimal with avg 85dB over an 8 hour period.  I use hearing protection while vacuum cleaning vinyl and have a decibel meter on my phone.  It's amazing how loud everyday activities can be.  Riding with the top down in my car is 105 dB! No radio.

On another note @mulveling - are you running the KT-88's in your amps and how much heat do they create.  I have the Sig 200's and they are warm here in Florida.  I will have to look closer at upgrading the amps as I have the Master Phono pre

The cut determines the decibel level.

When listening without any eq, the F-M curve is allowed to kick in and the volume control is used as a "focus knob", similar to a microscope or telescope, to determine the listening level.

Take a decibel meter to a live concert and measure a crescendo in a symphony. At home, match the volume to what you recorded in the concert hall on a recording of the same crescendo of the same symphony.