Differences in power vs power rating and such that you mentioned are what I, personally, would accept as things that would change the sound of an amp. However, I just have my doubts that well designed (ie, not Sony 5x100 BS amps) should sound the same at the same volume levels. If the amps are equally capable of driving the load of the speaker, they should sound the same.

Baah.

I am the Doctor, and THIS... is my SPOON!