1) I would think so although you would have to elaborate what low volume means to you. To me low volume is below -25 db which my wife still thinks is loud'ish.
2) You need a SPL meter. Radio Shack carries an inexpensive one however I would recommend a unit like this one which is far more accurate. I have it and it's good.
http://www.long-mcquade.com/products/556...e_SPL_Meter.htm Ultimately though, you (and your walls and picture frames) will feel 20hz in your body far more than hear it with your ears.
3) When you get to 20hz and lower you absolutely need a really good driver and enclosure. My EP500 works in this range (just barely though) where as my 10" Polk sub produces no output. You will need a 12" long throw/high output driver at minimum. Ultimately though this is EP600/800 territory. The large enclosure really helps.
Anyway, I am sure others will chime but these are my thoughts. However to be honest, my knowledge on these topics is quite dated and may not be totally accurate with today's speakers.
