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.