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.
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Totally disagree that a 12” is needed for meaning output below 50Hz. Many 8” and 10” options would be suitable for your situation as well. If you’re looking for subterranean bass then sure look at bigger subs. But to blend with the JBLs below 50Hz or so for music, smaller subs could work quite well. I think most people would be shocked by the KEF KC62s performance and it likely would be a great option. I think the REL T7 or T9 options would be a great match too. I personally use a JL Audio E110 and it will shake my entire room if I want it too. No trouble with output from that 10” at all.  And it has a wonderful onboard active crossover along with continuously variable phase control to make blending with the speakers much easier.  Fantastic sub.
How about a MartinLogan 1100x?  Downward or front firing, ARC makes tuning a breeze and the bluetooth app makes fine tuning from you chair child's play.  I'm running one with Heresy IV's with the crossover @ 58hz with ARC on and you cannot even tell where it is.  
cant' tell you how many times I've read audiophiles convert from 40Hz to 80 Hz and be amazed at how good it sounds. 
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Thank you to everyone with some really good ideas.   Today I ordered a SVS SB2000 Pro  12 inch subwoofer.  I should have it within a week and will post about it at that time.  I also ordered a cable from Blue Jeans to go from the output 2 on my integrated to the sub.  I think this will work out fine.