Subwoofer Recommendations


I am looking for a single subwoofer that will compliment my JBL L100 Classic speakers.  This is my office system and I only want 1 subwoofer (no swarm) to add a little oomph below 50hz.  I will be using it with my McIntosh MA6600 on the second set of variable line outs.  The sub has to accept line in, have a phase control, level control  and adjustable crossover so I can cross it over under 80hz or so.  I will be still running my JBL speakers full range.  Price is up to $1500.00 new or used although keeping it at around a grand would be great.  This is the only way I will hook up the sub and I would like something that does go deep.  I know there are probably hundreds of subwoofer threads but I have never looked at them.  This is just something I came up with today so any help would be appreciated.
128x128stereo5
You want low bass but have specifically ruled out the one most economical way of getting it. You will now proceed to spend more, probably even taking up more space, than the one method that will actually produce the low bass you want. Oh well.

Own goal is hard to image. So I go with http://www.vendoralley.com/wp-content/uploads/2013/03/shooting+yourself+in+the+foot.jpg
@maxwave, to an extent that is how it works ... the area of a driver (circular) increases exponentially with radius but a greater linear displacement also helps to generate bass at low frequencies.
The cone shape is also a factor.
One > two drivers double cone area and add to symmetry (power output).
Two > balances internal energy.
If you get hung up on 'driver envy' consider the fact that @ 40 Hz the wavelength is 8.6 M or about the same dimension of an interior wall (large room).
@stereo5, sealed enclosures have relatively good output response and if 
given good power will perform very well.
KEF produces extreme HiFi Gear and I personally would not hesitate to trust in the engineering some.
A single sub is smart ... not a mistake.
+1 @nonoise, good review article btw.
+1 @ozzy, Hsu is also very good and possibly a more affordable model.
How did you decide between the sealed vs ported sub on the SB2000?
The main reason was you were only looking for one sub so thought space may be a consideration and two SBs are a lot smaller than two PBs while still getting you under 20Hz (-3dB).  The other is I tend to prefer using a sealed sub for music, but I understand properly-designed ported subs can work as well.  Last, I own an SB2000 I use for HT and it alone can shake my living room when required so two PB2000s seems almost like overkill for music purposes.  So that’s where I was coming from with my recommendation.