This thread is recipe for failure.
First off, you need a pre-amp and source that is flat to DC (or at least 4hz @ -3db).
Do you even have that to start with?
You may want to take some REW line-level output measurements to make sure, before you waste any of your money.
You may just find out that you are rolling off at 10hz before it even hits the DSP or amp
(and then those rolloff themselves
Otherwise there is nothing there to multiply, right?
The FP14k is the flatest amp I know of (1.8hz) and an XSP-1 pre-amp and Xonar soundcard will be good down to about 3hz.
Ok that's $2500 and we haven't even started yet...
Hook that to an array of bass shakers or Rotary Subwoofers and you might just have some real world results.
That sounds expensive, because it is.
Messing with the amplitude and phase of infrasonic signals, at best, it is probably going to sound like mud soup, and at worst, create a dead subwoofer.
You probably won't miss much if you can already do 16hz. But hey, it's your money and your subwoofer, spend the money on creating a customized analog DSP infrasonic multiplier thingy and report back to us how it went