all i know is that the svs ultra cannot be beat for less money diy or not..... guy tried it with 4-15"s and double the power and got the same output. me ive tried building a different box for the setup and the lows jsut werent their. they put alot of work in their enclosures. take in mind the sub weighs close to 200 lbs i think its 190
and their $400 sub sounds really good to so you dont need to spend thousands. and yes the amp they use is different then the ones they sell on
parts express.
now stop fighting none of us here know how much is put into them or how much profit they make.