Thanks, Claudiu - I never thought of the option of turning AST on and off via the Beo5. I guess this will rule out the S/PDIF signal as all speaker will be active while using AST.
Elephant: I asked the same question on the Nordic forum and Peter Pan kindly provided the section from the manual describing how to use the speaker setup (see picture insert in original post on this thread).
I will get in touch with B&O as I would assume that most people would like to use their "big" speakers with the "big" picture, and provide a "Use Music Setting (3)" as well in their next S/W update of the BS3.
Thanks,
Roger