It's an Onkyo TX-NR808 which happened to die on new years eve. addle: It has MultEQ.
I just re-read Audyssey's own explanation of how MultEQ works and it sound like I found the answer to my own question. Audyssey works in a similar fashion as a Linkwitz Transform circuit in that it applies a mirrored opposite waveform to the actual recorded waveform during the setup to basically even the two of them out.
It would seem that with their description and the multiple posts I've seen regarding how Audyssey will boost very low frequencies going to any subwoofer, despite its limitations, in an effort for a nice smooth FR, I am hoping I'll be safe without any outboard processing and/or EQ for the time being.