Just saw this thread!

"I guess the question I am scratching my head over is: Is there Music Missing when you setup your system with no Center Channel?"

As others have mentioned I've always used the 950 w/ a phantom center (Newform Research speakers).
You lose no information (and I personally can name several points in favor of using a 'phantom center' over an acutal center. check out some of my comments on the SACD/DVD-A thread here if you're interested).

"I should say that under normal playing the system is calibrated such that I never get close to +10 db. I watch DVD DTS EX movies about -5db most of the time.-"

I watch at ~0-+3db for most DVD movies. I don't calibrate 0 to any reference db (most set it to 75 or 85db), but it's Very loud during the big peaks.

"-With the center channel set to NONE and playing a stereo signal through PLII, I find that I have to crank up the db. Does this make sense?"

Not really. I listen to most stereo CD's at about -12 to -7. This is all much louder than the average volume of the movies though because movies are SOOOO dynamic compared to CD's.

When I process stereo to DLPII-Music it is overall slightly quieter than the original stereo setting, but you seem to be describing a BIG diff. of maybe 10-20db though?

I find it to be more like ~3db. 5db tops, and I think this is basically due to a chunk of front info being routed to the back speakers.

In theory I'd think there shouldn't be any diff in SPL going from 2-chan to DLPII, but it does sound like it's a little lower.
No big deal... I just add ~4db of volume (though I don't really like DPLII that much. Kinda gimicky sounding on most CD's to me. I find while it's sometimes pretty cool sounding surround-wise the front end is also slightly degraded so I rarely use it. I think it's better than NEO6 though, but never compared to closely).

"The sub woofer seems to stop getting a signal in certain modes when you don't have a center channel. What happens to the LFE? Does it get discarded or distributed?"

That shouldn't happen. If you don't have a center chan. but you set the 950 to center -'small or large' then you'd of course lose information in a very critical and blatantly horrible way unless there's nothing recorded in the center chan, otherwise (like in my case) the sub x-over and LFE track are ALWAYS sent to my subs whether in Stereo, DD, DTS, DPLII, NEO6.

My system's 2.1 or 4.1 at all times.

Anway... as Gonk said you can't get 5 or 7 chan. stereo if you set the center to 'none'. Also as Gonk basically said.. this is dumb. My old Denon did it. No reason for the 950 not to.

Then again... I think 5 chan stereo's cheesy anyway so I never used it when I had the Denon.

"You will not see STEREO 5, STEREO 7, or the missing STEREO 4 remember (QUAD STEREO). I hear you may be able to get around this by going into different modes like NEO6 or PLII."

All you have to do is set the center to -small or large though and even if you don't have a center hooked up you'll be able to set it to 5 or 7 chan. stereo, and it'll be 4 or 6 chan stereo. Setting the 950 to DPLII or NEO6 doesn't really 'get around' Stereo 5/7. There totally different processing.
But much better, so I'd recommend you use either of the over 4/56/7 chan. stereo.

You do know what 5/7 chan .stereo is right? It sends the exact same main chan. signal to your rear speakers and a combo to a center chan. There's nothing audio qualtiy-wise going on there.

This is really only used by most people for party's to fill the joint with tunes, not for actual real sit down to listen to great music.