Subwoofer advice

I've had good results with Auralex SubDudes under the subs for isolation.

My experience with high-pass filters may be Ayre-specific, but I tried a Bryston 10B active filter and a Marchand fixed passive filter (4th order 80 Hz), both claimed to be balanced.  The Bryston really changed the sound, the Marchand removed a bit of the sense of air.  Both are gone.  I let the KEF Ref 1s run full range and supplement them below 40 Hz with pairs of Velodyne HGS-15s and HGS-10s and SMS-1 bass managers that provide acoustic room correction.

3. Best Performance system- Audio Kinesis 4-sub Swarm for $3,000. This option will clearly outperform the other options since it will provide deep, fast, smooth, accurate, highly detailed and dynamic bass that will be perceived as the most effortless, the most natural and the best integrated with your main speakers. It will also be the most convenient option to configure since all settings are made once on the amp/control unit for the 4 subs collectively rather than separately on each individual sub. 

Good luck,
  Tim

   I've respected your detailed and informative suggestions helping people new to subwoofers by sharing your basic knowledge and your enthusiasm with this system. I'm saddened to read your declarations of, "Best, most, and outperform the other options."    

Cry me a river.

Sorry m-db, don't get your post.  "saddened"?  Nothing wrong with having an opinion.  I welcome all information, and all opinions, as long as your not a d-bag.

@pkatsuleas --

... Looking to supplement clean low end not anything bloated or overbearing.

If you don’t mind going the DIY-route and being you have a fair amount of space allotted, I’d recommend you build 2 horn subs. My experience with them is this: horn bass doesn’t come any smoother, more articulate, enveloping and effortless, period. You get quality AND quantity in abundance, and the latter is equally important because it leaves you with tons of headroom, which means lower distortion from less cone excursion and in return cleaner bass. The better, and gradual coupling to the air via the horn loading equates into higher efficiency, but not least it has the cone movement excite the air more effectively (compared to a cone that loads the air directly) in a way that has the bass become more palpable/present, enveloping and nuanced - also at lower SPL’s. The only drawback: the physical size of the horns, but if you’re really into the best quality and can manage them, get over it.

Design recommendation: Lilmike’s Cinema F20 with the 15" Dayton RSS390HF-4 driver (currently $190 pr. unit at Parts Express). Make the cabs yourself or have someone do it. MDF will do just fine (certainly as a stationary solution), but plywood is better though more expensive. Get the high-pass filter poster @mcreyn recommends (or a miniDSP), and buy a cheap (but fully sufficient) pro amp like a Crown XLS 1502 (~$425 at Amazon.com). All this should come in at approx. $1500 total. Google named horn sub design for more info (where build plans can be had for free), and remember to make two of them, in case.

Seriously, no pair of commercially available pre-build sub solution below $5,000 (or even more) will beat a pair of F20 horn subs in the areas overall bass quality and SPL capabilities down to 20Hz. Some may go lower, but would lack in other, more vital areas. Importantly: substantial SPL capabilities isn’t so much about max. SPL per se, but rather headroom. Headroom is your friend, and a surplus of it will give you totally effortless bass that I’d wager only horns subs can provide (and if you high-pass your mains, as recommend already, it’s all win-win).

Just my $0.02..