Subwoofer Decisions - REL/Rythmik, Pair/Single, Paper/Aluminum Driver, etc.


I have decided to upgrade my subwoofers. I have a 15x12 room with an open side wall that I use for 2 channel and HT. Two channel music performance is the priority. We don’t listen to either very loud or need the room to shake. I am considering the REL S/510 and the Rythmik F12, F12G, FM8, L22 and E22. I have an all Linn vintage system. My speakers are Aktiv by installing special crossover cards in the 5 channel Class V amp. It outputs to the speakers in a bi-wire configuration. If I used a high level speaker connection I guess I would have to tie into the speaker wires connected to the Bass/Mid card.

Any thoughts on Rythmik v REL? You seem to get a lot more for your money with Rythmik and they also offer more options - finish, sizes, configurations, etc. Supporting a Texas based business is also nice. Do they offer equal or better quality and performance? There seem to be many fans that think so.

Any thoughts on Rythmik’s paper v aluminum drivers? The owner says that the aluminum driver retains its shape faster and is more detailed. He recommended the aluminum in my system over the paper even for 2 channel. The paper is lighter and has better extension above 80Hz. I’ve also heard that it is better at low volumes because it easier to move. My current subs have paper drivers and paper seems to be greatly preferred in the audiophile community.

Any thoughts on pair v single sub in my size room? One 10 or 12 is probably enough to pressurize the room but will a pair of dual 8 or 12’s make everything easier and better? Is there a point where they will overwhelm the room?

Things are pretty tight in my room so the smaller footprint of the vertically stacked FM8 and L22/E22 are appealing. Also stacked drivers look badass right? The FM8 with its dual 8 inch drivers will probably be faster than the larger 10 and 12 models. It also appears to go plenty low enough to keep up for basic HT needs. The L22/E22 have a smaller footprint than the single driver F12 but I’m concerned that those might be overkill.

High level speaker connection? REL recommends it. Rythmik offers it but recommends using other methods. Anyone know if using it with a Class V amp and tying it only to the bass/mid speaker output will perform well? I’m not sure how REL implements its filters to make this work. Is the high level connection really better in performance?

Thanks for the help.
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“Two channel music performance is the priority”.

A pair of REL’s s/510 would provide seamless integration through high level connectivity and superlative bass for 2 ch & HT.

Brace yourself...subwoofer discussions here ends with no consensus!
The a crossover with high pass is the most important part. With a good crossover you can greatly improve your sound. With just a low pass you are just extending the bass (which is fine too...but not as good). Two subs will be much better. One sub can work fine for a single seat but it is much harder to get right. I would take two cheaper subs over one pricy sub every time. 
I can’t comment on the subs you are looking at. I have never really demoed subs back to back but l like sealed high powered subs for music. 
Interestingly I have found that all most all the speakers I have tried crossover best right around 60hz. Something about 60hz seems to optimize both the sub and speakers. Maybe not forcing the sub to play too high or the mains to play too low. Not sure but this has been with multiple speakers and rooms. Anyway give 60hz with a high pass a try.  
Also keep in mind that speakers will cancel out the bass 1/4th the wavelength to the rear wall. If you put your speakers 4ft off the wall there will most likely be a hull at 50-55hz. You can place the sub less than 36” (from the driver face) from the wall to avoid this cancellation. Another options is bring everything more than 6’ off the wall to avoid bass cancelation but this is not practical for most.  
Here is a chart that can help. It will be quicker to calculate it for a starting point. Between 3’ and 6’ the bass with have major issues but this is where speakers should go for soundstage and midrange tone. But placing the subs (less and 36”)  and speakers in different spots can fix it. 
http://www.soundoctor.com/freq.htm

This video might help too. Not exactly related but will make more sense than my rambling lol. 
https://youtu.be/T10_MLGOBfc