There are two most essential principles to audio amplifier design. The first is simplicity. The second is linearity.
Simplicity is a common element of the best and most subtle designs.
It is preferred for purely aesthetic reasons, but also because fewer elements color the sound less, and lose less information. Many audiophiles, including myself, are willing to sacrifice other areas of performance to achieve the intimacy with the sound available through a simple circuit. An amplifier should be simple, but it also must be linear. Some measure of distortion in an amplifier is unavoidable and forgivable if it is of a less offensive type, but still it is important that the measured distortion performance be reasonably low. The advantage of a simple circuit is lost if the sound is overlaid with an excess of false coloration.