Paul, despite the suggestion in the manual, leave the setting at 8 ohms(even if you were using 4 ohm speakers)unless in the highly unlikely circumstance that the receiver would keep shutting off. The 6 ohm setting limits the amount of voltage available at the rails in the power supply section of the receiver and therefore also limits the maximum power available. The form of Ohm's law relevant to this is I=E/R, i.e current in amps equals voltage in volts divided by speaker resistance in ohms. A lower impedance speaker therefore would allow more current flow(possibly causing overheating)at the same voltage, so the lower impedance switch or setting cuts down the voltage. Don't worry about it, the 1400 can handle 6 ohms at the 8 ohm setting with no problem.
