Re: too many subwoofers!
Def. look into Treo subs, best of what you listed.
I had the Premier 3004 (Model before the pioneer u have posted). It sounded good and got fairly loud, but isn't on the same level as the others.
As for the cadence, a friend of mine had two 15's of theirs. Not that model, believe they are 1 or 2 notches below, rated at 750rms each or so. Got loud, sq was iffy. Had 1400rms on em and they blew in about 2 months
Subwoofers: 12" Soundsplinter RL-p
Amp: Hertz EP1D
Enclosure: 2 Cubes @ 32hz
Refs: dropped_mazda, muffinman944, KCha, pioneerpimp, Looney_Tune, Ion SQL, IamMurph, stevexyz, dsmw, waccord99, snb778s