Correct, Andrew; at the same sound level, within the designed limits of each unit, there would be no audible difference. All that any amplifier can do is to amplify with audibly flat frequency response and inaudibly low noise and distortion. This is routinely accomplished these days in relatively moderately-priced units; there's no special magic in putting the amplifier in a separate box.
Claims of the "more detail" sort lack factual support when the volume levels are equal. Of course if one is set slightly louder, more detail is heard simply because it was louder, but this isn't a valid comparison. This is why in blind testing the volume levels are matched to within 0.1dB. When this is done neither "detail" nor any other sound characteristic is audibly distinguishable.
