What most people descibe as "sweetening" is in fact a sort of "smearing" of information that the amplifier is processing. It can be compared to saying that an impressionist painting is "sweet" compared to an accurate photograph of the same subject matter. This works OK with some subject matter, especially when some other parts of a system are producing distortions that are not pleasant to hear. Smearing those distortions, or "sweetening" them, may be desirable to some extent to cover them up.
But do not lose sight of the fact that the amplifier is NOT accurately reproducing the signal it gets; it is a form of distortion, nevertheless. you are never going to get really fine sound until every component in the system is free of the distortions that the amplifier is to some extent masking. The fact that ugliness looks better out of focus is hardly a good solution to preventing the ugliness in the first place.