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

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. 

That depends on how many cocktails you have .I guess...

@jonwolfpell 

I find it funny that so many people listen at levels where their amps, even with very inefficient speakers, are barely putting out a watt or two or maybe 10 on peaks. What’s the point of having big powerful solid state monsters if that is so? 

exactly. I’ve said this many times to the dismay of people who say (usually parroting what their dealer told them) something along the lines of, “but it provides more grip” or “but the transients come out better with more power”. 
 

If you are listening to 2 or 3 watts, the 50th watt or 80th or 405th watt are literally not even being created or accessed whatsoever. Just use a true RMS meter on your speaker wire and see for yourself. Press the “peak hold” button and see the highest number that gets hit. It’s that simple. 

it’s typically the higher power amps have a different component mix that changes the sound. You replace 0.6mm low mass wire with 2mm thick buss bars and 4x the power tank capacitance and that’s gonna change the sound.
 

 I’ve built many amps and power supplies and learned this first hand.