Thadman, have you consider the Seas Lotus subwoofers yet?
I have two buddies, one use to have a 12" Ascendant Audio Avalanche, and the other one use to have a 12" Diamond Audio TDX. They also had a 12" IDMAX there after. When we switched out the subwoofers for the Seas Lotus sub, it sounded better with no tuning applied. It was just a straight trade (box too) hooked up to the same amp. In both cases, the Seas Lotus sub were more musical and smoother. I would have to say the Seas Lotus is one of the most underlooked SQ-oriented driver.
I'm in the process of getting rid of my IDMAX for one too //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif
Though it doesn't have the output of the avalanche or the IDMAX, it gets plenty loud for an SQ system. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif