I am considering a Velodyne DD-18...

...to complement my Joseph RM25 siII speakers. When I went looking for speakers with more bottom end the dealer who sold me the Josephs said that in my room, 16'X13'X9', I'd have trouble with resonations. He suggested that a sub that could be tuned to the room would give better results. After much reading, I'm gravitating toward the dd-18 but I have heard it said that a smaller room may prefer the dd-15. I assume that the dd-18 will better reproduce the very, very bottom end and that the equalizer eliminates the issue with the room size. Anyone have opinions on the above? Thanks for any replies.