SUBWOOFER to match Focal Chorus 816V's?

Hi,

Looking for opinions for a dynamite musical (yet pounding bass when appropriate) sounding subwoofer to match my Focal 816V's? Thoughts? I like my low end bass ~ but only want to spend around $1000.00 or less either new or used. Not in budget for the Fathom 113.

Thanks! Dill