Thanks for the tone suggestions, John. I actually found a nice little shareware program that creates test tones and sweeps (Audiotest - for Mac). Created a cd of test tones in no time. I also have a Telarc recording of Dupre, Franck and Widor organ works that I'll have to give a spin.
After some brief test tone testing:
14hz - virtually no output
15hz - Some tactile output, not enough to rattle anything unless I venture way above 0dB
16hz - Getting stronger - vibrations throughout the room
17hz - Very solid output - vibrations and rattling like crazy
18hz-20hz - It looks like the PB10 really gets into it's comfort zone in here.
So, solid bass output to 17-18hz, with useable output to 16hz? Not bad, not bad at all.