As someone previously mentioned, there's no "normal". The volume depends upon the source, your room size, room treatments, and speaker efficiency.
For comparison though, I've got my 667 in a 20x27 room with carpet and an 8' ceiling. I'm driving Axiom speakers.
For movies, I set the volume to -20db. Most of the time I keep it there, but I might move it up or down a bit by a couple db depending on the particular movie.
For some music I'll go to -15db.
For regular TV...