What is the best subwoofer you have ever heard?

Mat, I've never heard the Paradigm but considering your needs I doubt it will fail to impress.

IMO, a good subwoofer can do both HT and two channel very well. To accomplish this with sensible connivence the sub needs some form of modern signal processing with presets that can be switched via a processor, pre/pro, receiver, or subwoofers, remote.

Even if its a dedicated HT or a two channel system the media usually needs its varying share of EQ such as phase or gain. The more control you have over your sub at the listening chair the more you'll realize just how important a sub can be.

If you have an older surr amp, go for sub including eq system. Audyssey Pro with my own way of measurement gave the best integartion of a sub in stereo as well in Multi channel use I ever heard!

I have demoed the JL 110, and they will be my next purchase. They sound great!

See if you can demo some JL Audio and Velodyne subs. F113's, Gotham, DD18 plus or 1812. Very impressive.

If I were you, audition two SVS SB13 ultra subs - 45 day trial. I have a PB13 Ultra(best sub I've owned and heard) and i'm going to try a SB13 Ultra, decide which I like better , and get another of choice. Depending on your room size, 2 SB13 Ultras cost you the price of one JL audio F113, 4 will cost you the price of a Paradigm Sub 2 in price. If cost is no object, I'd get 2 Paradigm Sub 2's and calibrate them and be done.......so done.......