I have a RadioShack SPL meter also.
Average SPL measurements at my listening position, 12 feet back from the center of the speakers is;
Enjoyable but loud listening levels: 93 to 96 db
If I turn it up (exceptionally loud): 105 to 108 db
These are average levels, without clipping and, as far as I can tell, without any audible distortion. Peaks are typically 10 db higher.
Note: I never listen continuously at an average of 105 to 108 db as it is uncomfortably loud and ears will ring afterwards.