Lots of theaters run too loud, and dialog often suffers as a result. That doesn't mean it's an example of what good home theater should sound like - on the contrary, it's another reason that I rarely go to theaters anymore. I have personally handled calibration of the "theater" in my den and I have the volume control in my hand.

The Radio Shack SPL meters are the standard tool for these purposes. It's sufficiently accurate. I've used one to calibrate my system and other people's systems numerous times over the last decade or so.