Paradigm Signature Servo vs REL B1 / Stadium III

I have a Lexicon with Merlin vsm speakers driven with a parasound amp. The room is 15 x 15. I use the system 70% for home theater - movies and 30% music. Which of these, or others?, subs do you recommend. I have about $2k to spend. The local dealer has the Paradigm floor model on sale for $2k. It seems I can buy the above REL's used about the same.
THANKS!