Maybe you should consider consulting Michael Green from Michael Green Audio. He tunes studios and concert halls. Getting lowest lows right is tough. He has a strong reputation in the pro-audio world. Your room as it is does seem to be messed up.
Proper Room Acoustics/Designs
I have the chance to build, from ground-up, a new listening room. I have spoken with Dennis Foley and have learned much, concerning the proper room dimensions, as well as room designs. Instead of adding room treatment devices to deal with room nodes etc, I will be constructing a great room from the beginning. Has anyone had any experience with him directly or indirectly? BTW-I started with the Analog forum, because there is no forum, that I know of, that deals with listening rooms. Any suggestions?