I have a onkyo SR 504 at reasonable volumes it sounds fine but i when i crank it up to 60% + volume the sound starts to break up quite a bit.
I am sure the Yamaha Amp design is as robust as the onkyo. I have been running this SR504 with the MK for over 3 years now with no problems(Touchwood)

. I did not like the DSP quality of the onkyo, i feel the decoding is lacking detail and clarity in output when compared to other brands.
Therefore planning a switch. Also my room is 60% reflective, not many curtains or furnishings.