We just switched from Yamaha (stereo only) to h/k, with a modest AVR147. We are very happy with our unit and have had no quality control issues at all. We did a side by side comparison with the Yamaha in stereo only, using two identical front speakers on each unit, and played each unit at different levels from -33dB to -16dB to -10dB (much higher than normal for us, and really too loud). We immediately noticed a slightly smoother sound for the h/k and a much more pleasant listening experience at high volume levels. We wondered if this was because the Yamaha was distorting at those levels, making things sound just loud and noisy. Since then, all fully hooked up in 5.1 with Polk Audio and an Acoustech H100, we have found the h/k to be excellent for our needs.
I would not say that this means that harman/kardon is better than Yamaha (or Onkyo), but it was an interesting first experience and we certainly get more out of our old speakers now.
By the way: Onkyo have had issues with Audyssey EQ setting the crossover too high (120 or even 150). You might want to check this since it apparently affects sound quality quite noticeably. Harman EzSet/EQ set our crossover to 60Hz on modest little MiniMonitors (and an excellent CS245i center).