Ok, I just took some SPL readings at my listening position. My SPL meter is a Galaxy Audio CM140, its a lot better than the standard radio shack SPL meter, but it isn't great for burst measurements (neither is the RS meter),so if I had been doing serious burst tests with my Earthworks mic and MOTU preamp, I am sure I could have measured higher SPLs. So continuously, I can sustain about 119 dB at my listening position from the Defiance X15 using a 55 Hz sine tone, maxing out at 119.8 dB. The C-weighting at 55Hz wouldn't be much different than no weighting. That's as loud as it gets continuously at my listening position. I would never listen to it that loud outside of a brief test though, that is absolutely jarring, plus it scares my Cockatiel - which is on another floor of the house. If I feel like getting crazy and listening to some oldskool drum'n'bass at high levels, I can't imagine ever going over 110 to 114 dB at my listening position. Keep in mind music is complex signal and not a pure test tone, and those are two very different animals for any kind of loudspeaker and also will have different loudness sensations for human hearing. But regardless, that is still a very loud range and it puts a pretty good beating on just about any sub. Bottom line is the X15 has more than enough dynamic range for my needs, and I am pretty needy when it comes to bass.