Definitely keep the speakers matched, it'll look better. Ceiling or wall mount really is up to you, whichever works better in your room. Don't forget you can "flushmount" the QS8s with the included T-bracket on the wall or get the optional full metal bracket which would allow you to change the angle of your surrounds and bring them away from the wall somewhat. \:\)

Half of communication is listening. You can't listen with your mouth.