That's my question for shkumar4963 as well. Why no center? A decent center channel speaker is far more important for movie playback than rear channel speakers.
If you you have trouble with unclear sounding dialog without a center speaker, and if you don't have the space for one, it's time to make some space.
I haven't listened to a system with a 3-6 dB boost in the 150-600 Hz range, but I strongly suspect it will alter the sound of your front speakers for all sound, dialog or music, without solving your problem.