Been asked before but... One sub or two?

Please - before someone tells me to read past threads, I have.  Still hoping to get some response to my specific situation, so thanks in advance.

My current listening room above my garage is approximately 15' D x19' W x 8' H with hardwood floors and drywall walls.  There is no room treatment other than upholstered furniture and an area rug, My speakers are approximately 9' apart along the long wall, 3' from the front wall to face of speakers, and 9' from my listening seat. Wall behind listening position is mostly windows (no curtains).  Speakers are Focal 1028BE (34hz-40khz~3db) on Gaia ll feet, with just a few degrees of toe in.. I also have a single Focal Chorus SW800V sub (32hz-160hz~3db) in the corner of the room along the same wall as the main speakers. Speakers are driven by a Marantz PM-11S3 (100w/200w @ 8ohms /4ohms).

 This sub was from an earlier system. I am trying to decide whether to upgrade and, if so, given the relatively small room size, whether one or two subs is the way to go.  My preference is a single sub that will complement the Focals but reach down closer to 20hz.  My budget is $1k-$2k.  Thoughts?