There is little agreement about whether technical differences among amplifiers are reflected in sound quality. The most relevant test of this, double-blind listening comparisons, are so much trouble to conduct that they are rarely done. So, what it comes down to is acquiring a set of prejudices that let people arrive at conclusions in the absence of relevant evidence. My suggestion: Don't believe anything.

Greg
VP180, M80s, M22s, QS8(4), CSW S305s, EP500, Pioneer VSX-90
M2i, M3(2), Pio vsx-1020