Yup, all that done. I have also played offending material with 2 channel only, then shut off mains and unit still has "power vibrations-distortion" like it has bottomed. I also tried same thing while bending over and lifting sub to make sure no extraneous vibrations from floor contact and same result. Unit sits on concrete slab with heavy marble flooring here in Florida, so no resonance in the home structure. Have to believe unit should perform at half volume (my guess about level where problem starts) without distortion. Guess I should return for another unit. On this sub, if you advance the volume to max it shuts of the LFE completely, and hence the receiver should be the boss and it is indeed set at 80hz.....have also tried at 60hz and same distortion.