I have a design in mind, have bought a speaker building book, etc. I want a high end system either two way or three way that has good punch in the bass and can go down to say in the lower 30 hz range. I have researched speaker specs and read and reread the chapters on volume and tuning. These speakers will be a ported design around 72" x 15" x 15". Some questions, 1. If I use two woofers (say 2 10" drivers) do the drivers double the required volume? 2. Would two 10" drivers or two 8" drivers give better punch than a single 12" driver? Thanks for your help. I know some of this may be sketchy as I offer no detail of the driver I'm considering. I'm simply looking for "a rule of thumb".