As for 10dB, in fact, I have not read a proper analysis of this, and this 10db number relates to very old perceptual tests, of which I have not been able to find the original research and go over it's conditions(just 2nd or 3rd hand mention of it with no real details provided). I can say that to me and a lot other people I know, 6db is a huge difference with music, perceived, and to me it sounds like roughly 2x. 10dB is an incredible increase to me.
-Chris