Red Orc,
Wid is correct. Whatever you're setting to 4 ohms, don't. What that does is limit the voltage/current from the receiver/amplifier's internal power supply to the output transistors, severely reducing the amplifier's maximum output power and dynamic range. That may be what's happening with your setup. You may be running the amplifier into near clipping or distortion, which might account for the problems in sound quality. Set it to 8 ohms even if you're driving 4-ohm speakers. That will help prevent the amplifier/receiver from going into "current limiting".
And be sure you turn off the auto-equalization.
Regards,
Alan
