Small or large sub for music

I'm firmly in the "DSP robs the music of some soul" camp (I don't trust the sonic opinions of the designers...how do they know what I want to hear?), and think a normal room (meaning with furniture, rugs, and stuff other than traps and damping panels) can sound great. If you live in a steel shipping container with no furniture you have other issues to worry about that DSP ain't gonna fix. Using 2 subs takes care of a lot of the aforementioned room mode issues if they're receiving the same signal (not stereo) at the same time...it just works. Also, if sub levels are too loud, turn it down. 

Remember that good subs don't simply add bass reinforcement, but contribute to the overall listening experience by adding life to the mix. Live concert halls and even studio mixed recordings have lower frequencies adding an ambient and more lifelike "feel" to pretty much everything, and although your speakers might not "need" this, I know I need it for things to sound like real music. My current Heresy IIIs are great at producing realistic sounding bass within their range, but really drop off at around 58hz or so...my subs take up the rest and the resulting overall low frequency coherency and "room charging" gets the mojo right.

Why does anybody care if the bass is distributed evenly around the room? Is this so you can enjoy accurate bass while doing your yoga headstand against the wall? Weeping about things in the corner until the housekeeper finds you? I use 2 subs that seem to help cancel some room standing wave issues, but I do serious listening from my specific sweet spot (like most audio geeks) which is where stereo mixes actually work. If anybody wants to really appreciate my rig along with me, it's necessary they sit in my lap or stand behind me while I sit in my "magic" spot. Also, it's possible to get great (and musically rewarding) sound from one sub as this is generally better than no sub at all. Movie sound is the McDonalds of audio...lots of salt and fat to make you feel good initially, but it has very little to do with good food...as a reference for audio, film sound is a ridiculous mix of extremes that isn't really designed for music appreciation. If you spend your time listening to and enjoying the digital reproduction of Army tanks and explosions, you're unique and hat's off to you!

I've been in the actual music biz for over 5 decades...back when we used Altec A7s (extremely efficient) we typically ran maybe 200 watts into the bass speakers and 50 to 100 into the horns to make things balanced. Now I use 1500 watt powered bass systems, with maybe 350 watts per side for full range main speakers. Look at meters for output on home gear and you get the story...bass frequencies take up a lot of juice, even with efficient speakers...they simply do.

Bass frequencies absolutely require MUCH more power than treble or mids, to state otherwise is ridiculous.