I have a MARANTZ SR7007

Ideally you will run Audessey first to get the levels right, then "0" is supposed to be Reference level after that point, which theoretically should be 85 db with 20 db of overhead, a max of 105 db, which is ideally how they're designed to be listened at, although that is really friggin loud in my opinon as well as many other people's opinion.

Of course every movie is different too and can vary wildly. I typically watch movies at -20 but "Looper" sounds more like other movies do at -15 or even -20. I can't watch Star Wars at -20, my ears will ring for awhile, but most kids movies has to be that for the dialogue to be understood well.

So, it just depends on your preferences, what movie you are watching, how sensitive your ears are, and how seriously you take hearing loss.