Sub Pairing With Harbeth 40.3 XDs

Hello all - was wondering if anyone can recommend a sub pairing that is commensurate with my Harbeth 40.3 XDs ...? I love it loud. Looking for tight , punchy thump from the kick drum that sounds like arena PA ...🥳 

my system : 

Manley Snappers , Manley Jumbo Shrimp Pre

Some of these Subs like the REL S/812 seemed kinda pricey....an Emminence $250 speaker in a shiny powered cabinet doesn’t seem worth $3200?

Thanks!