Not sure what active Sub to buy need help!

Just brought 2 Kam RZ12A V3 Active PA Speakers 2000W 12." I'm not sure what sub to buy and can one sub work with both speakers. Obviously i'm running them though my Behringer Xenyx 24-Input Mixer. How would i connect the active sub to the setup and which one is best for those speakers? Do Kam even make active subs? 
EAW and QSC make great subs but KAM is a low cost brand so I am not sure it is worth using a higher end sub.