Merlin VSM-M and Bass

A bit of background:

Equipment:
Marantz SA-14 SACD player
Sonic Frontier Line 2SE preamp
Belles 150A Hotrod amp
Merlin VSM-M with BBAM

Setup and room:
diagonal placement
speakers about 5-6' apart and fairly close to the side walls in a 20'x20'x10' sloped ceiling room with a big opening into a 20'x12'x8' kitchen

I bought the Merlin's (VSM-SE) about 2 months ago and had Bobby upgrade them to the Millenium w/ BBAM. My question is how can I get more bass from them? These speakers are (were?) going to replace my Revel F30. The Revel's have the bass that I'm looking for, however, from maybe 100Hz on up, the Merlin's are much better. I just do not get the bottom end that the Revel's put out.

Integrate a sub? And if so, any suggestions?

Thank you,