Ok........so when we hear something, we hear the direct radiation of the speaker elements and the reflected radiation at different points in physical distance and of course, time. We also hear resonances created by physical items in the room in what is known as the modal region. So what finally arrives at our ears is a three dimensional recreation of the original signal created by the speakers and the room.....yes?
So if an amplifier should be designed to be uncolored or neutral to the original signal, how does an amplifier impact imaging or soundstage? It's frustrating to have to work backwards through these discussions but hopefully I've made this a bit more clear for some. One could of course make the arguement for crosstalk through channel seperation but that's really easy to check for. Of course if the amplifier is broke, replace it or have it repaired.
This is NOT to say all amplifiers sound the same. In regards to dynamic capacity, distortion products and noise floor all of which can impart a difference that may be audible under certain circumstances but NONE of the above will change the radiation patterns of a speaker OR the reverberant field of a three dimensional space as both are mechanical parameters given a fixed signal path.