If the music was recorded with surround channels I'm inlined to use them, but I tend to avoid the derived surround modes the Bryston SP3 processor can generate. I use KEF LS50s for side and rear surround.
Who Uses Rear Surround Speakers For Music Playback?
I feel a very slight surround fill improves music playback. Similar to a subwoofer I set it low enough that you can't point to the sound source. I've found the smallest/affordable speakers in the rear are able to make a noticeable difference. What is your opinion on this subject?