lack of clarity when using Audyssey XT

[natetg57]

I have Sierra's across my front stage powered by a Denon 991. I'm using Audyssey to process the sound and use an Epik Legend sub with music and movies. I have homemade bass traps in three corners. I want just one setting for everything. I'm generally happy with the sound I'm getting. When I listen to rock/progressive music I like the sound of 'MultiEq Xt'. It seems to thicken the sound. But with classical, such as violin or piano with orchestra music I seem to get a cleaner more natural sound with Audyssey turned off.

When I ran the autosetup I used all 8 positions including two on top of the back of the couch near the back wall (1ft away).The other thing that I noticed: when I played a disc of test tones I noticed that frequencies from 100hz and up varied quite a bit as I moved to different positions on my couch. (my main listening position)

So, I'm wondering if Audyssey is trying to compensate for a null(s) in some positions (such as in front of the couch which is near the center of the room) and therefore boosting 125hz and 250hz and muddying up the sound.

I've also tried MultiEq 'Flat' and thought it sounded a little too thin and/or harsh.
Thanks!