Yeah, Adrian; maybe the Denon manual was a bit confusing on the point(surprise), but when there are only two surround speakers in a 5.1 setup, they have to be used as side surrounds rather than back surrounds. Then, to listen to 2-channel material in more realistic surround sound(which I always do), you apply ambience extraction such as DPLII or Neo:6.

-----------------------------------

Enjoy the music, not the equipment.