So I found this mini-review:
http://forums.audioholics.com/forums/threads/emotiva-erm-6-2.55541/
Which says that these speakers are sealed and rated down to 80-20Khz +/-2db.
This tells me that these need two things a) 90-100hz crossover point and b) A very capable and accurate sub, able to play flat all the way up to 120-150hz. These beasts are not as common as you think, most even good subs just play up to 100 and "give up", take sharp nose dive.
Is this is your sub:
http://www.audioholics.com/subwoofer-reviews/csx15-mark-ii ???
If so, Josh Ricci, the authority on measuring subs (check his site at
http://www.data-bass.com) wasn't very impressed by them.
You may just need a new sub, like this one (or two to help deal with room modes)
http://www.hsuresearch.com/products/uls-15mk2.html
If this doesn't help, then you may need new speakers. I have nothing but respect for TLSGuy and his audio system(s), but Jeff from JTR Speakers may also know a thing or two about building capable speakers which will play to 11 and far beyond that
I particularly like this video:
