The whole Audyessy debate is very simple. Play around with setting it up a few times and if you like what it does then keep it, if not, don't sweat it and disable it.

I've done the latter. More to the extreme of resetting the receiver and re-calibrating with a SPL meter like Alan suggested above.
I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne