I'm not trying to be rude or anything, I'm curious. What is the difference from the SA-8 SA-10 SA-12, and SA-15 they all can produce about the same db 150 ish single sub. I'm wondering because I just bought a SAX-1200D amp and I was going to get the SA-15 but now I'm unsure what to get. I'm looking to move some air.. Thanks in advance.