If anyone wants a great example of panning effect try the film MISSION TO MARS. There's a scene where the camera does a 360degree turn on a room while a man's voice is heard coming from a communication screen in a spaceship. As the camera pans (turns) around the room the voice moves from front center to front right, to surround right, to surround left, to front left and back to center. The film is in 5.1 but decodes well in 6/7.1 adding another placement for the voice to be heard as the camera pans.
And because it's the same sound/voice it is a good sample for testing volume levels as well.
BTW - I have M80 and 150 and 4 QS8s and timbre quality is excellent - with the only real difference heard is (as previously mentioned) probably the room and how how it affects the sound from each speaker location - which is normal with sound in general.
