For over 20 years now top tuning has been one of my favorite tweaks. It is the cornerstone of electronic component grounding and without it listeners lose tons of the music. You can find a lot about top tuning by visiting www.tuneland.info where many of the great tunees spent time talking about their listening adventures.
The basic principle of top tuning is gathering the energy from the top of surfaces and sending them to ground along with the energy that is being transferred by gravity. Because of how weight works there is much energy that sits at the top of components vibrating loosely causing distortion because this vibration is not in tune with the energy that is heading out the bottom of a component. This distortion leaves your soundstage fussy and undefined. There are some that believe in killing vibrations all together but this causes yet another type of distortion "omission of the signal". by top tuning we can find a balance between the energy flow up and down to make the vibration of the parts easier to put into tune eliminating signal path vibratory distortions.