Two-channel is inferior to multi-channel, no?

I agree. I worked a long time to avoid excessive manipulations/dynamics. But I have never ran into a situation where multi channel was too flat (?) Just the opposite from all my experiences.

JDL-

Mds,

You may be experiencing a bad case of combing/cancellation, when your speakers cross paths. Try aiming/ or re-locating your center channel differently. Or possibly experiment w/ the distance setting on your center channel. Get the L/R speakers sounding great. Then introduce just the center channel next. Once you find a synergy here....add the surrounds one set at a time. This is the only method that I could get to create a harmoneous mix. Also experiment w/ a different surround mode. Neo-6 works well for me.
Just some thoughts....(?)

MC that is flat w/no depth ?? Is your processor broke ?? This is exactly what I use my center channel for....to create extra depth, dimension, AND HEIGHT. I cannot stand some recordings where the singer's voice is coming out of the baseboards of my room. It gives me a sense of being in the nose-bleed seats....looking down at the performance. My center channel speaker is located @ 5 1/2 feet off the ground. This raises the recording's height to start with. Then I tell my processor that it is located three feet closer than it actually is......so it will delay the center channel's arrival time. This creates great stage depth and ambience. It seems to stretch the depth of the stage, so I get better seperation between the singer.....and say the drum kit. Sometimes it sounds like the singer is directly in the drum set ?? Once I have a synergy between these three speakers, I begin to add ambience w/ my surrounds. I use the left surround and right surround speakers as "height left and right speakers". They are located to the far right, and far left of my main L/R speakers, near the front wall corners. Their sound must come from a height higher than the mains. This creates an illusion of more depth and dimension for your sound stage. My back surround L/R speakers are located above ear height (4-5 feet)......just slightly behind my listening position. I point them just a bit behind my head, so they are not directly on axis to my ears.
My center channel volume is @ 10% to 20% less than my L/R main speakers. I spent a long time dialing in this center channel volume and distance. It is the most important part of getting multichannel music right. Again, you must get the three L/C/R speakers sounding perfect, before introducing the L/R surrounds, and L/R back surrounds. All surrounds are run at a volume 30% to 60% less than my L/R/C mains. I have them set to a volume where you cannot realize their location. All these volumes depend on the surround mode you decide to use.
I will usually tell the processor that my sub is located one to two feet farther than it actually is, so it will allow for an earlier arrival time. This depends on the speed of your sub. This correction seems to keep my sub in time w/ my other speakers. I use the actual distances on all my surrounds.
You have to spend alot of time dialing in these distances, and volumes. If a speaker is allowing you to hear its location......it is not set right. Ocassionally I can hear my left or right main kinda standout, if there is a hard L/R pan in the mix. But I do have my main L/R speakers spread apart by almost 10 feet. So it does happen sometimes.
I use this set-up for my red-book 2 channel music, as well as my surround. My Oppo BDP-83 SE decodes all SACD, multichannel DVD-A, BluRay, etc. 2-channel music is recorded onto Flash Drives, and played through my Bryston BDP-1 player, and decoded thru Neo-6 on my Krell S-1000.
I can honestly say 2 channel sounds anemic, and not nearly as robust.....if not processed now.
As a few others have stated, the center channel must be of equal or higher quality, than your main L/R speakers. Your center channel amplifer must also be of equal sound quality to the mains. Your surround speakers can be of lesser quality in my opinion......but not junk.
All of the varibles I have mentioned above are severely affected by your room acoustics/dimensions. Distances and volumes must be experimented with, before you find the magic.
I have given up trying to obtain that "being there" sound quality. After owning a live music venue for over 20 years, I find stereo systems fail to produce the dynamics of a live performance. Acoustic events can be duplicated more easily. But in my opinion, the recording process fails to deliver the "live music event". So if the source is incorrect, there is very little hope to re-create such.
And I wish more recordings would put the bass player either to the left, or the right of the artist. That is reality in almost all stage sets. Too many recordings have the singer and the bass player standing "inside" the bass drum doing their thing.....or so it sounds ??
Of course all of this is my opinion, and what works for me. Many audiofiles hear my system, and think I have one of the most kick-ass 2-channel systems they have ever heard. They do not realize it is multi-channel I have switched on. I for one will never look back to 2-channel again.....