Kevin, I've gone over this several times previously and it isn't simply a matter of my take on the question. Audio engineering principles require an amp to be flat enough in frequency response and low enough in noise and distortion so that any slight differences which are measurable are inaudible. This is commonly achieved these days at low cost and that's all there is; no mysterious effect on soundstage, etc. exists.
Once labels and price tags have disappeared in blind listening tests differences which were previously described in lavish terms have likewise disappeared. As Dr. Toole once commented to an AES meeting(relating to the fallibility of human perceptions), when you can see what you're listening to you can't hear it.
