Dude, if you make a parallel connection to two M22s, using their nominal 8ohm impedance results in a net 4ohm impedance. Also keep in mind that speakers dip below their nominal impedance at some points and that at those points the effective impedance would be below 4ohms. Whether this would cause the receiver to shut down would depend on the volume and the length of time for which this effect lasted. It may work out fine and could be at least tried.

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Enjoy the music, not the equipment.