Who are some of elite sub woofers?

I have one SVS SB16-Ultra and really like it.  I had the SB13-Ultra for about a year when the SB16 came out ... I simply traded it in for full purchase price and upgraded to the SB16.  Very good customer service / trade-up policy.  I'd add this one to your list if you are one of the "masses" or if your interested in a reasonably priced subwoofer on Stereophile's Recommended List "A".

@larry5729

It’s a subwoofer, impossible for it to have soundstage depth, unless talking stereo use with each sub playing either the left or right channel.

mzkmxcv"It’s a subwoofer, impossible for it to have soundstage depth, unless talking stereo use with each sub playing either the left or right channel."

This is a Statement of Faith and for that reason, logic, and explanation by definition there is no arguing, disputing, or challenging the poster’s Faith or his Belief. However it is easily contradicted, invalidated, and rendered false by actual science, engineering, and experience but some people like to reference a "Book" to explain, justify, or rationalize their Beliefs, Convictions, and Practices. Say Hallelujah!

For music I run 2 subs. Both have 2 12s Dunlavy brand, .  Recently For movies I add in I bought  6 15 woofers and. Built boxes and got a mini Dsp to help with standing waves and get placements better.   Without it some areas have insane bass while others non bass.   Didn’t realize how it worked till added in the low bass movie subs   Can get a lot of bass with diy     I’m pretty happy with the Tannoy woofers running off crown amps for movie lfe 

I'm guessing this subwoofer is to be used in a two channel music system?

Multiple subs will defiantly load or pressurize and reduce or eliminate room nodes within a listening environment better than one. With proper placement and equalization you should find very enjoyable performance at your listening position.

Regarding your budget I suggest you look into Syzygy Acoustics.

http://syzygyacoustics.com/#

Unfortunately, their site doesn't seem to offer their manual for the possibility of slaving your current 12d from the remote controlled room corrected Syzygy or running two of their 8" models. I'm sure they'ed be happy to answer your questions. 

In my opinion room correction is far more valuable than giant driver size. 
Good luck with your search and have fun.