OK, the Outlaws fixed it (thanks Steve).
As hoped, it was a simple setup issue caused by me having the rear speakers connected to the "back" 950 outputs instead of the "surround" outputs.
(gonk...in hindsight it makes sense. When I tried the Dolby EX test using the 5.1 source it could not decode rear information because it did not get a real EX signal...even though I forced the decode)

So, for everyone else...although it is not clearly specified in the manual, for a standard 5.1 setup the rear speakers should be connected to "surround" on the 950...even though you might have them located at the back of your listening area.

OK...back to listening !!