Wow! I put on Clapton: Unplugged, turned the PLIIx Panorama off and wham-o...no more wrap-around effect. But it sounded muddy and not as defined as stereo.
So I kept tweaking. I had Dimension set to 4, I bumped it to 6, and for whatever reason I got deeper bass...slightly deeper than stereo mode and definitely deeper than direct (the 600 was on by the way).
My fronts and center were set within a couple of dB around zero. So I turned down the left & right to -12 and the center to -9.5. I noticed that the bass was now pounding. I turned the sub from -6 down to -12 (the lowest it can go) and it was still too much. I had to dial it down on the back of the 600. Also, the sound-stage was now deeper...not wider but definitely deeper like the experience I reported on Oscar Peterson in Neo. And Clapton sounded too laid back and about 4 feet behind my foundation wall
. So I turned the center up to -4.5 and he came forward but in general the soundstage was deep. By deeper, I mean deep behind my fronts. I already had depth between me and the fronts.
Then I switched to stereo and lost quite a bit of the depth behind my fronts and lost the bass but this felt far more rocking than before. I can't say that I liked stereo more than PLIIx. I'd have to say that the choice depends on one's mood.
Then I put on Oscar Peterson. I found with this that I was getting the wrap-around effect again even though I had Panorama off. So I dialed down the surrounds from the +4 for the sides and +8 for the rears to 0 and +2. The wrap-around effect disappeared and I got a nice broad and deep soundstage very similar to the Neo that I reported before.
Then I put track 3 of Dead Can Dance: Into the Labyrinth and I created an instant cathedral. I turned up the volume on the surrounds and the cathedral grew by leaps and bounds.
So after Johnk's suggestion to turn Panorama off, I am now much happier with PLIIx. I don't know if I'll use it on every album but I will definitely try more of it and experiment to better understand it. I love the way these surround modes give depth behind the fronts and expand the soundstage on some recordings.
What does the dimension setting do by the way and why do I end up with more bass when I turn it up? Also, it appears that even though I have my cross-over set to 80Hz, the M80s still put out a lot of bass that ends up cancelling with my 600.
I'd also like to hear from others if they get a deeper soundstage behind their fronts when using these surround modes with their front speakers turned down. I am sure this has a lot to do with placement of the surrounds and room acoustics.