musical subwoofer recommendation for 2-ch

I have had experience with REL and JL Audio subwoofers. Both are highly regarded here on Audiogon. My REL Storm III subwoofer was connected to the high-level speaker outputs on my power amp, but could also be connected to the line-level outputs on my preamp. My current JL Audio Fathom F113 hooks only to line-level inputs. IMO the REL was easier to integrate with my Wilson WP7's, but was more limited in bass impact than the JL. The JL has a lot more adjustments but you would probably have to work harder to get it to integrate with your speakers. The JL has a lot more impact, especially on the low end, and you can actually hear the pitch of bass drums. In either case it was possible to integrate them so that I could not hear it separately, but only could tell it was on when I switched it off and then realized what it was adding to bass impact and spatial detail. IMO the lower the frequency you roll it off, the better subwoofers work, as they work best when adding what your main speakers are not capable of, or as in my case, I only use it to pressurize and de-pressurize my room. So if your main speakers roll off at 70 Hz, I don't think a sub will work well going up to 70 Hz. There are those who think a pair of subwoofers work better but I have never tried it.