If you can hear significant differences in sound between those three receivers identified above, then I would suggest that the settings on each of them are different, especially the volume setting. Good receivers, or preamp/amp systems should sound the pretty much the same. And what's one of the most important characteristics of a good system - it's the power supply. The heavier the unit, the better, because they more than likely put in a real power supply, rather than a crappy switcher.

Eric G.