Damping Plates

Lots of discussions about isolators and couplers used on the bottom of components but not much said about dealing with internal resonances using damping plates on top of the equipment. Harmonic Resolution Systems (HRS) is one of many manufacturers that make such devices but, like all things with an audiophile label, they can get expensive. Low-cost alternatives such as scuba dive weights have been mentioned by some.

Have you tried damping plates and were there worthwhile improvements in sound quality?