Musical subwoofer under $2000

I’m looking for advice on what vendors to look at as l’d really like to add a subwoofer to my 2 channel setup. The room is c. 30x15 feet or 42 square meters with low ceiling of about 7.5 feet or 2.2 meters. Budget is c.$2,000 and my 2 channel speakers are Sonus Faber Sonetto VIII. My amp offers pre-out connection. I’d like REL but their S range is now too expensive, so something close in musicality would be great.