When you calibrated the unit, did you calibrate to 75dB at the 0db volume setting? Some of the Polk speakers (which look to be what you have based in the pic in your sig) are on the low-side efficiency-wise, so if you are running up around +1 to +5 in some cases you may want to verify your calibration and possibly even calibrate to a higher reference level (maybe 80dB at the 0dB volume setting).