I actually have blocks under most of my equipment. I have a tendency to dismiss most of these tweaks, as other factors, such as speaker location, and just adequate power for playing speakers at the level you like seem to make a much greater difference. Was there a difference? Not a lot to my ears, much less that moving my speakers or listening position a few feet.
Have not tried this yet, but thought about steel/lucite/wood balls embedded in some blue tack might be another cheap way to try something else.