Angel, welcome. In your size room M22s should be excellent, along with QS4 surrounds. As to whether a 7.1 setup would be worthwhile, it depends more on your distance from the wall behind you than on just the size of the room. If there would be at least 4' behind you for a back surround effect to develop, then it should be considered. If on the other hand you'll be right up against the back wall, then stay with 5.1.

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Enjoy the music, not the equipment.