Looking for a musical subwoofer @ $500>

Had some thoughts, but figured I would ask here as I was given some great advice for my previous amp/preamp questions: https://forum.audiogon.com/discussions/amp-preamp-or-avr-for-home-stereo-and-entertainment

System sounds great btw! Parasound A23, Integra 80.3, KEF Carina II's, Technics turn table, and a Blu Ray Player. 

Anyhoo - I could use some more bass. The KEFs get down to 55hz but a lot of my music goes lower and I don't want to compromise... to a point. 

Looking for a sub capable up 25-30hz on the low end with anywhere from 8-12" driver for less that $500. I came across the Klipsch R-12SW and the reviews were stellar, especially for the price. Want this for music more than Home Theater, but both would be nice. I've even read that the Pioneer SW-8 or 10 is a fine unit for the price. 
I know of names like Sunfire and Velodyne, but I wonder if it's worth buying into those companies if I can only afford the lower end products.

Also, my guess is that buying a used subwoofer is like buying a used race car... expect it to be driven, hard. 

Thanks in advance!
Looks like a nice one. Any others to look at? The room is will be in is approx 12' x 14' x 7' high
Don't know the starting prices for Hsu and Outlaw, but they are two companies, (along with SVS), that are specialists in high quality budget subwoofers.
I believe SVS has a generous trial program (45 days in home with free shipping BOTH WAYS!). I'm not familiar with the Hsu or Outlaw in home trial.
 SVS also have a nice tool, (Merlin), on their website to match your speakers to their subs, it is fairly exhaustive in terms of main speaker listings, but I don't think your speakers are on the list. I would give them a call at their 800 number and get a staff recommendation. The online tool not only acoustically matches several sub choices to your main speakers, but they typically are a good match "budget wise". My take on SVS is they don't try to oversell. Another option is to try a couple of Pioneers, or Dayton subs (Parts Express), as two subs should provide 
Whoops sent my response off before it was finished by mistake.
Two subs may help achieve a smoother in room response and more output. I would be surprised if the two "cheaper" sub option would be as well built as the low end SVS or HSU subs. I would also compare warranties, vendor knowledge/advice and tech support.
So I've boiled it down to HSU VTF-2 MK5, SVS SB1000, Outlaw UltraX 12. They range from $500-650. I'm going to call SVS in a moment, but in all likelihood they will want to sell me an SVS sub, so, with that in mind, any final thoughts? 

Appreciate all the help.
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Hsu - I have the VTF1 MK-III (2 of them). I find them quite musical with my Maggies. They are real easy to integrate.

" I’m going to call SVS in a moment, but in all likelihood they will want to sell me an SVS sub, so, with that in mind, any final thoughts? "
What do you think they would try to sell you??
Well, yeah, I realize that, donvito101. I had some questions and they answered them. I also called Crutchfield and had a chat. Went with the SVS, go figure. They had one available for $450 (open box, brand new otherwise), so I got an Audioquest cable, too and still came in under $500. That'll do!

Thanks y'all
RELs are brilliantly designed, sound great, and use your main amp for the signal (the "High Level" input...so they arguably sound like your amp).  I own 2 from the same era…a Q150e 10" 150 watt, and a Q108 MK2 100 watt. Both were bought used for around 200 bucks each and work perfectly, and feature adjustments for level, phase, crossover points, etc., that many other brands don't have. They're known for their "musicality" and having had mine for a while used with various power amps, I can say they're an indispensable part of what is the best sounding rig I've owned in over 50 years. Be patient and look around for one of these as you can't go wrong with 'em.
I like Rel subs. You want a fast sub maybe with a servo amp. I used to have SVS but the customer service was not that great when I wanted to fix it. I think Rythmik subs are very good as well, with fast amps built in (thinking F12g).
My two cents...
I strongly suggest a Vandersteen 2WQ. On-board 300 watt amp, adjustable, allows your amp to work solely on your mid and treble, and clears it up considerable. $1m600.00 but you can find previously owned for $500.00. I did. If in S. California, try Stereo Unlimited. I think they have one., so you can listen to it.  Otherwise, they are often on Audiogon.