I was looking for a subwoofer to complement the Kef LS50. The LS50 is an extremely good loudspeaker for the price, when combined with a good amplifier and cabling. However, you miss low below 50Hz.
First bought the B&W PV1D because of the reviews, but it was difficult to get it working together. Sent it back (Coolblue is so easy!!) and tried the Kef Kube 12b, again because of the reviews. I was a bit hesitant, considering that it costs half the B&W, but it fits together wonderfully.
There are heavier subs available for movies, but for music this is really spectacular. You don't hear that a sub is on, but when you turn it off, the sound becomes thin.
DSP settings work great. It's in a corner of our living room, which is far from ideal. But the DSP on corner and everything is right again.