Are your listening levels healthy? Doing damage?

Do you know decibel levels when listening to your system, and how loud do you go?

Since upgrading my system, again, I find my listening levels have tended to increase. Not because I'm slowly going deaf but because it's more enjoyable.

I measured the decibel level with a few iPad Apps, and there was lots of disparity. Plus or minus 25 dB. 

Certainly if it's too loud I sense things are not healthy but I'd really like to know how loud things are since Google tells me prolonged listening above 70 dB could be damaging my hearing.

The apps on an iPad are clearly unreliable and now I have to contemplate spending several hundred dollars for a sound meter as well as a calibration device so I can know what my limits are and so I can be in compliance with Google.

Anyone know a good sound meter, and do most serious listeners get one of these things?