I'm not pointing to any particular cases referred to in this thread where people indeed hear differences. I'm simply saying that – I believe - if one were to take 2 amps/receivers, set them up properly as to exactly match dB output, and switch them such that the listener does not know which is playing, the sound differences would disappear. It's been stated before, the mind is a powerful thing, and the placebo effect should not be underestimated.

You can test your theory re preamps by connecting the Emotiva amp(s) to your receiver. Match the levels with an SPL meter, and have someone switch the 2. This will take the preamp processor out of the loop. Unfortunately, if this procedure is done manually, there is a lag between switching which brings audio memory into play. However, I believe you have indicated the difference in sound between your receiver and new set-up are dramatic, therefore even if the switch takes 20 seconds, you should still be able to test.