I was a bit surprised by the QS8 surrounds. Does 120 Hz sound right? My concern is whether my EP500 can fill in the full range below 120 Hz. Will the EP500 fill in the upper end of the bass below 120 Hz - say from 80 Hz to 120 Hz? This also applies to the VP150 which is set for 110 Hz
I would try repositioning your speakers trying to take advantage of boundary reinforcement from walls corners with your QS8s and the front wall or cabinet walls for your VP150. This might help your Denon detect them as going lower. Also trying different microphone locations as suggested might also help.
If that doesn’t get you lower numbers I would at least try lowering the crossover from 120 to 110 or even 100 for your QS8s and to 100 for your VP150. At least that way the speaker will try to play a little more of what would otherwise be a large dip in SPL above 100Hz where the EP500 drops off like a rock. The tradeoff is that there is no Audessey curve calculated below where the Denon set the speaker. Given a choice of no Audessey curve or a deep drop in SPL I would do without Audessey over that small frequency range.