Just out of curiousity, how far have you turned up the subwoofer? Have you tested any of its limits?
We managed to push the SVS PCi 16-46 upwards of 100dB at 50Hz and decided not to venture any further. Besides, some of the SPL WAS coming from my drop ceiling at that point. How much we could not tell but i'm sure at least a dB or two.

"Those who preach the myths of audio are ignorant of truth."