I think high SPL is dangerous and should be kept to a modest level and modest time period. However, too loud for the wife doesnt mean too loud IYKWIM. I have also heard that the higher the distortion, the greater the potential for damage, given the same volume level. Bear in mind that most distortion comes from the speaker, even before clipping.

 

more distortion is definitely worse for your ears and, your speakers and mostly! your pride! even if you hit a distorted 150db's a solid 150db's would sound way better. Even a clean 148, i hate when i hear a stereo thats all loud and distorted especially one that doesnt even push 130db's....another petpeeve of mine is the people that drive cars and use a remote!! a remote is only 2be used when the deck is out of arms reach, or from outside the vehicle

 

I work with small engine construction equipment most of the worning dB labels on these machines start at 80 dB to 110 dB and state long exposure to those level will cause hearing damage and the long exposure is based on an 8 hr work day.
But when it comes down to it it depends on the person and the shape of the ear whitch catches the sounds.
For those that know me my ears are large and stick out cause i have very little cartilage which helps form the ear.
So 110 dB can cause damage in a work day where your out in the open then imagine what what 140 dB can do in the confines of your car.

 

I think I read somewhere that the human ear cannot hear distortion until it is at 17%.