Seeing your fight with Audyssey and members here, I might probably do the followings just in order to scrap out some points.
1. Would go to Hometheatershack's REW forum, show them the graph, especially the boost in the low frequency region and carefully describe the way you have the measuring gear setup and calibrated. I have a fear there is someting in the way you are doing the measurement that results in such a low end boost, but maybe (probably) in real life it is not there. Especially that you have mentioned that the phenomenon exists for all speakers in your system, not only for the center.
2. While using REW, I would engage Generator, setup a log sweep and listen carefully to that lower range in question to hear and compare to the higher range whether that boost is really there for your ears or not. A 10 dB boost will clearly be audible.