I bought the YST-SW012 to go with it. It's not too big, but still has a lot of "bang". On/off and level are on the back, which can be a drawback if you have to use it often. Not the case for me, so it doesn't bother me. I would buy this combo again, I'm happy with the result.

I bought the YST-FSW050 for this purpose. It gives the sound a good bottom. I can recommend it.
I bought this subwoofer because of the dimensions and because it has the control buttons in the front, but I think any Yamaha subwoofer goes well with it.