REL Subwoofer. Your input requested

If your goal is bass that is articulate, tight, fast, powerful, and deep, then the number of subs is far more important than which sub. No one sub can match four reasonably good ones. Nothing else with subs is anywhere near as valuable as if you can learn that one basic truth.

Now as for how its connected, does not matter. If the sub has speaker level inputs that are convenient then use those. Or if the sub has line level inputs that are more convenient then use those. Got it? Nothing matters less than which one you use. Well, except for balanced, which will matter only in the sense it gets you to throw away money on something that's an absolute total waste when it could be spent buying something that's not quite a total waste.

Save your money to buy more subs. Thank me later.

I have the REL S/5 SHO and it's terrific, as is the REL connection system, though I did get the REL upgrade cable...

strenckr,
I sent you a PM. 

@strenckr,

The High Level Input on REL subs is not a marketing hype or a gimmick...it works amazingly and provides seamless integration of REL subs with your main speakers.

You didn’t provide your room dimensions so it’s hard to recommend one 212/SE or a pair of say S/510’s. From my experience, two subs are better than one. But then again, depending on your room size you may be able to pressurize your room with one 212/SE.

I am using a pair of REL Carbon Limited’s and couldn’t be any happier. I switched from a single JL Audio f212v2 to REL’s.

I have 2 RELs of the same older vintage (a Q150e 10" and a Q108MKII 8"), both bought used (200 bucks each), and although maybe 10 years old or something (not sure) they work perfectly. The "high level" input is the one to use as it replicates the tone of your power amp, although at lower frequencies that may not matter much. The very high impedance applied to the amp means they're basically invisible to the amp relative to their drain on the speaker signal. The single Q150e worked really well for a couple of years, and when I bought the Q108II things worked even better as multiple subs playing the same signal help each other to conquer standing waves (depending of your room of course), and generally just make things work more effortlessly. Great little woofers.