Yamaha HS8S Active Subwoofer

I wasn't sure if I should buy this sub to complement my HS7s, but I'm glad I did. I use my setup to listen to the music and watch movies, and it drastically changed the experience. First of all you really feel the music – the lower frequencies are reverberating in your body, even on very low volume. In general I noticed that I can listen to the music on a much lower volume and still enjoy every detail. It also gives presence to such instruments like double bass, tuba, drums, or lower octave of a piano. My HS7 no longer have to deal with these lower frequencies and at least to my ears sound a bit clearer.
One thing to keep in mind though is that it's very sensitive to the positioning (like any sub). If I put it in the corner a bit out of sight, then it creates a room mode in the opposite corner with greatly amplified bass, while there's almost nothing in the centre of the room. So need to play around with it, and adjust for your listening position. Something to keep in mind.
Overall very happy with the purchase.