That makes sense, but one more question, if you don't mind.
What made you decide to go 2 x 12, instead of 3 x 8?
I might be going OB Bass in the future.
Also not Jay but I chose the 3x8 for two reasons. First, in their current location, I needed the smaller footprint of the 3x8 vs the 2x12. Second, since I was building the bass units for my Wedgies, I plan on re-purposing the drivers and amps into the wedge bass Danny is working on once it is finished.
While both will play just as low (flat to 20Hz, -3dB @ 14Hz) as I understand it the 12's will do it easier with more authority and presence (two 12's have a little more surface area than four 8's). That being said, the two 3x8 H-Frames are no slouch. They can bring plenty of bass.
Cost wise there is very little difference (~$140) between four 12" drivers + two A370PEQ amps and six 8" drivers + two HX300 amps. Since the cost is so close, it really comes down to what you need. If you want the most output and don't mind the larger footprint, go with two 12's. If you need a smaller footprint or have other design considerations that would favor them, go with three 8's.
Either way you will end up with some awesome subs.