The speaker impedance switch is commonly used on receivers to compensate for the limitations imposed by fitting the amps in the same chassis with everything else. In fact, I've even seen some receivers in the 1070's price range omit the switch by restricting the amp ratings to 6 ohms or higher (basically saying that they make no guarantees that it'll drive a 4 ohm load). I wouldn't worry about it for a 6 ohm or 8 ohm load.