Here goes - not sure how this will go down, I know it's expensive and has been cheaper way back, but this is the cheapest i can find at the moment.
Ideal with your Play1 and Play3 speakers or for those setting up your home cinema using Sonos Speakers.
* Adds dramatically deeper bass to any Sonos speaker (or amplified component).
* Zero cabinet buzz or rattle.
* Versatile. Place it anywhere. Standing up or lying flat.
Not sure between the Gen1 or Gen2, as I can't find much info.