There are so many great subs on the markets, especially when optimized by the SMS, Aerial, Velodyne, Talon, SVS.
While I can not speak to the synergy of the SW-12 to the Merlin, I have successfully integrated the SW-12 into a JBL K2 system, several Aerial systems, Energy Veritas 2.8's, Snell Music and Cinema Towers but not successful with Cello Grand Masters, B&W Signature 800's, or Wilson WP7's.
Hope this helps.
The SW-12 is an AWESOME, AWESOME sub!