Rel t9x or Rythmik F12G

Small room. I’d go with a pair of REL T5x. I have REL S3 and love them. Even though the 5x are small, they work well in a small room. You don’t want to overpower the space.

Complete no-brainer... Get the Rythmik F12G and call the trash guys for Rel disposal.

+1 for a pair of REL T5x.

I have a pair for my little AR M1 speakers, but I also use them when I’m using a set of Tekton Pendragon in my 12 x 18 room. Easier to set up to blend with the mains when you use two subs.

If you listen to a lot organ music then maybe get the Rythmik :)

I’ve had both and would go with Rythmik.  I’ve had many REL subs over the years and enjoyed all of them except the T9x.  I had a pair and just could not get them to sound good.  The Rythmik goes a lot lower also.  My experience with the T9s made me question their quality and price to performance ratio.  They market their new aluminum drivers as an upgrade but I think their old doped paper/pulp ones are better.  At around $1100 shipped the Rythmik are a tremendous value.   

I agree that for music only and in your small, square room I’d do two smaller subs versus one larger one. Your speakers go down to 38Hz (-3bB) and the T5x doesn’t go much lower than that, not that there still wouldn’t be benefits but with your speakers I’d be looking for a sub that brings more low-end info to the table — and there is very important info down there that greatly improves things like imaging and soundstage in addition to just more bass capabilities. I’d recommend trying a pair of SVS SB1000 Pro subs that are relatively small (about 13” square) yet still go down to 20Hz (-3dB) so it’s a true subwoofer with the benefits that brings. Plus they come with software that lets you more easily integrate the subs from your listening chair with your phone (which is really nice), and they offer a totally risk-free, 45-day trial including shipping both ways so if they don’t blow you away just send’em back. Last, a pair will only cost $1150 that seems to be within your budget. Read the reviews that are quite positive. Just another option to ponder, and best of luck.

I run a pair of Rel T5's, a Rel T7 and a SVS PB200. Haven't heard the Rythmik, but I am sure they are great. 

My only comment would be that you don't default to merely placing one large sub in a corner and calling it a day.

Buy two subs minimum and place them where they work best. A common problem is that people will buy a pair of subs and proceed to place one beside each speaker. This does nothing to help the low frequency response in your room, as it will only accentuate any peaks and nulls that currently exist. By placing the additional subs with a purpose, one can achieve low frequency nirvana.

Thanks for all of the advice and hope to decide fairly soon. Will give my impressions once I get a chance to experience the difference.

I highly recommend Rythmik servo subwoofers, which can probably control the expected low-bass reverberation problems in your small room. They include superior adjustable EQ, which works better than phone-controlled stuff. Your small room does not need two subwoofers; if you disagree, you can always buy a second one. Don't assume there is a "best" spot--just move a single around and put it where it sounds best, probably away from walls.

I haven't heard the T9x, but had Rel Storm III and replaced it with two F12. Way better and cheaper. Eventually (about 6 years later) went with four F12. This gave a way more even response, plus more body.

I would go with one F12 and see if later you want add another. 2 is generally better than 1, 3 better than 2, 4 better than 3 (Unless you have total freedom in layout - then 3 is probably enough).

Rhythmik all the way.  I ran them with Magnepans and it was amazing.  You have to spend a lot more money on the REL to best the Rhythmik.

@noromance OP is using Klipsch Fortes in a small room. He's already overpowering the room. Be that as it may, and much as I love the REL T/series, they're simply not a good match for the Klipsch. IMHO in an 11X11 room first he needs acoustic treatment and bass traps, then rethink the entire speaker setup. With something more to room scale for both the mains and subs. JBL 4309 and REL T/9x comes to mind.

The Svs sb-3000# are very well built and have tight bass and a great app to control 

and $100off on a pair. Free shipping 5 year warranty and I think a 45 day review period.

Amazing how someone can state "already overpowering the room" without any evidence.  I'm currently using a REL S510, located in my room's primary bass node, which is located right next to my seating position.  Completely invisible with my Forte IVs.  Considering adding two T5's. When properly set up, RELs can be a great addition, without "overpowering the room.?

@ric2001 

You can easily start with one T5 and see what you think.  

I highly recommend Rythmik servo subwoofers, which can probably control the expected low-bass reverberation problems in your small room. They include superior adjustable EQ, which works better than phone-controlled stuff. Your small room does not need two subwoofers

@condosound Other than the fact that I also highly recommend Rhythmic subs there’s nothing else here I agree with. First, the “phone-controlled stuff” that SVS offers incorporates the considerable benefits of DSP (as almost all better subs offer now) and has the ability to control far more than Rhythmik currently offers. That you can do it from the listening chair rather than running back and forth from the sub to the chair is a considerable convenience feature. Rhythmic is just really behind the ball here when it comes to incorporating DSP into their subs. I recommended the SVS subs for their size, performance, DSP, price, and their generous trial period along with their excellent customer support. That said, at a similar price I wouldn’t hesitate to also recommend the OP consider a pair of the Rhythmic L series subs or even better the F series if they’re in budget. Both are larger than the SB1000s, which may be a consideration in a smaller room.

And the size of the room doesn’t determine how many subs are required or optimal, and as most experienced folks here have recommended, two subs are better than one for many important reasons and four are better than two if room logistics and budget allow.

I’ve two Rythmik F12 and a pair of REL T/9x in my 2 channel music room. Rythmik’s on the from wall. One REL on each side wall. The Rythmik’s are much less costly, more detailed, and greatly more adaptable. Rythmik build quality and cosmetics are as good as REL. I’m selling the RELs that will be replaced by another pair of Rythmik’s.