What Subwoofer should i buy to the Sonos Connect Amp?

Really ? Statements like that suggests you've had every amp on the market today or at least heard a good variety.

I've had the connect amp myself.....sent it back pronto as a cheap vintage Sony receiver sounded better to my ears. It may be good for bookies in a smallish room, but I'd look elsewhere to drive towers to higher spl's in a medium to large room.
Really?
I have owned about ten of different makes ranging from a 20wpc tube one to a 250wpc solid state and heard maybe as many more.
Which amp of up to 55 into 8 ohms wpc did you find that sounds better? If yes, did that better hold up in a level matched DBT?

The purpose of having this site is to give neutral suggestions based on what sounds better. It seems there are couple of guys giving sonos recommendation on every topic.

I'm afraid I need to disagree with you. This is a Sonos owned and operated/moderated website, not a neutral site like the AVS forum. You should expect to get a significant amount of Sonos feedback here.

If you're looking for unbiased information, you'll certainly get some here, mixed in with the Sonos based information, but you should not expect purely unbiased data on one company's support site.

Agreed 😠