"So, idmax is agreeably best sq sub on the market" Not between everyone. Some people still argue that the W7 is the king of all SQ woofs. You've also got subs such as the Focal Utopia, Rainbow Vandiums and even Boston makes some pretty good SQ subs. It's really all about your own tastes. I've never heard the ID MAX personally, but from what i've heard it's defintely a top dawg in the sq department.
"but leaning more towards spl in baby steps - we got: 1. RE 2. Brahma 3. ?
...right?"
It depends on what RE sub you're referring to. The SX and MT line are most geared twoards SQ. As for the Brahma, it's not an SPL subwoofer, nor was it designed to be. It's a long throw driver designed to have great output while maintaining excellent SQ. If you're looking into Adire for SPL, look into the Tumults. Obviously the Kicker L7's and Solo X's come to mind when I think of SPL subs. However, I can't really see why you'd waste the money on the Solo X unless you've got tons of money, and want a sub stricly for burps and no musicality. Incriminator audio offers some good SPL subs with their Lethal Injection and Death Penalty series. Also, can't forget about Digital Designs. They make some of the best SPL subs on the market. That's a few of the ones i could think of off my head right now..i'm sure i'll think of others. FYI, they were in no particular order.
I whould look into JL 12w6v2 or the ID MAX 12 for SQ drivers. If you port either of these subs its known to have good SQL. For more of the SQL mix, dont forget the Avalanche 15 by ascendant audio. For all out SPL i whould look into Degital Designs 9500 and up and also RE MT.
the MT is strictly SPL the SX is a good SQ sub, but due to it's efficiency and throw combined, it will produce more SPL than the XXX with a given amount of power, so it is their best SPL goal sub below the MT, which is made for nothing BUT SPL events.
An aperiodic enclosure is a type of IB(Infinite Baffle) sub setup. The membrane, usually made from fibreglass insulation one side of the box allows the sub to move air. The amount of Fibre iunsulation determines how the enclosures tuned. The enclosure basically allows air to move freely through the back of the sub when a woofer plays low fequencies, but doesn't allow air to move through on higher frequencies.