I thought about the IDMAX, but I've heard about a bunch of problems with them.
Haha sorry if I sound like that, but the more I researched, the bigger my list actually became.
Digital Designs - Basically the God of subwoofer manufacturers, but other than that I don't know much else about them
RE Audio SE - Heard the Quality is pretty good, but the loudness?
RE Audio SX - LOUD, but Quality is just ok
Fi Q - All-Around Amazing SQ sub... but again, how loud is it?
Fi BL/BTL - Again I heard mostly SPL sub, but SQ?
The reason why I made this post was to see if anyone could make some cross-comparisons between them, as I am VERY indecisive.