It is hard to say what you mean by "soundstage isn't very open". To me that usually relates to speaker positioning and toe-in, not the EQ, unless room acoustics are causing issues. However, the gain seems a bit low, implying the amplifier is adding more gain than the AVR can compensate. Is -12 dB the lower limit? If so, it may be the balance is off. You could try not using the amp and seeing how it sounds, and/or adding a line-level attenuator before the amp (assuming the amp does not have a volume control).
"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley