Marigo Labs Mystery Feet (3) - $380
Extremely RARE on the used market.
Crazy good under all electronics or speakers!
They are the best resonance control devices for amplifiers, preamps, DA, electronics, I have ever encountered.
Their sound signature is neutral, but the drop in the noise floor and increase in clarity and articulation was greater than I expected.
There was also an increase in soundstage height. INCREDIBLE!!