You're talking about only a half octave range at most. I wouldn't be concerned about it - all Auto EQ systems have a finite number of control points, it is not possible to EQ every frequency from 20Hz - 20kHz. These systems EQ in ranges of frequencies. For example, if the receiver (Audyssey does not set the crossover point, it just takes the measurements) set it at 120, and you dropped down it down to 100Hz, that small range of frequencies in between would just be averaged and no human could possibly hear a difference in that range between eq'd and non eq'd.
The crew at Audyssey will also tell you to manually lower the crossover point....