I've recently calibrated all my speakers and subwoofer using RadioShack Digital SPL meter. I also used the tripod at the listening position and set the meter to ear level height on the 45 degree angle.
For the test, I used Terminator 3 DVD.
I left the dial at 100db settting on my RS SPL meter. In T3 the nuclear explosion in the chapter one was very loud. I set the Master Volume at -10db below Reference Level and I measured 105db SPL! peak at my listening position. This is the highest reading so far in my HT theater. I don't listen that loud personally. My favourite is -25 to -30db REF which gets me around 85-90db SPL peaks.
SAFE listening is the BEST listening!