Well, for what it's worth, the ICBM could remain in the system you described, since all of the modes offered by the 950 that generate surround back data (Dolby EX, DTS ES, and CES) do so in a mono format. You could set the 950 up for 6.1 and let the ICBM split the surround back channel into two for the rear surrounds without losing any information.
So basically 7.1 really isn't 7.1 but 6.1 with an additional speaker?
As for the popping sound, I'm a bit less useful there. The most likely candidate in my mind for this is the interface between DVD player and 950, and it sounds like the changes you've made are all downstream of the 950. Are you always in surround modes that provide a surround back channel (such as CES) when this happens? If so, can you drop back to straight Dolby Digital or DTS and see if it still does it?
Yes, all changes are downstream of the 950 and player, less a new coax cable I installed which I will replace with the old, just incase.
First thing, like you suggested, I will drop back to a 5.1 sound field and see if it continues. If it does I will shut down the new amp I added and go from there.
I was running all 4 rear surrounds off one amp and I may return to that set-up if all else fails.