Are you sure that such setting gives more current (as it would with a transformer) or, simply, more protection for the AVR (as by introducing a protective resistor)? Both are known to be but I do not know what your AVR does.
Every receiver I've seen that has a separate 4 ohm setting usually does put a resister in series in the output.This reduces power,but also helps protect it from the low resistance load.In other words,it helps keep the amp in the receiver from overheating,and getting damaged.One way to tell if this is the case,check the power rating for all the channels driven times 8 ohms,and 4 ohms with all the channels driven at once.If it doesn't double,or have a large at large increase at 4 ohms,it probably has a resistor in the circuit. Checking the Integra site,it obviously uses a resistor because its consumes a maximum of 972 watts total including thermal losses. This seems to be common with a lot of receivers.Integra link.[http://www.integrahometheater.com/model.cfm?m=DTR-50.1&class=Receiver&p=s]
The power output is rated for 130 watts @ 8 ohms. The dynamic power rating is 150 watts @ 8 ohms, 250 watts @ 4 ohms and 300 watts @ 3 ohms.
It sounds like the setting probably is more limiting in the 4 ohm configuration because it has the potential to limit the power output in order to reduce the load on the amplifier, correct?