Dano, let me suggest that using one of the surround ambience processing modes such as DPLII or Neo:6 with stereo program material generally results in a more realistic effect than does applying all-channel stereo. The all-channel stereo mode simply duplicates the left front sound in the left surrounds and likewise for the right side. This is often suggested for a party, etc. to make the sound levels more consistent throughout the room, but doesn't attempt to get a totally natural effect.
Using DPLII, etc. on the other hand extracts from the front channels only the reflected ambience mixed into them that came from directions other than the front, but had to be put there because there was no other channel to put it in. This is then directed to the surrounds to duplicate the live listening experience a little more closely.
