Yeah blueranger, it is not for enclosure damping that I use the VPI Brick, but rather for absorbing stray fields from the amp's transformers. But the mass of the Brick makes damping products unnecessary. Another product for dealing with those fields but without the mass of the Brick is the Shakti Stone.
Geoff's questioning of the audibility of electronic enclosure vibrations and resonances is valid. But they can't help! In a perfect world, hi-fi electronic enclosures would contain no vibrations, whether from transformers, acoustic waves from loudspeakers, or seismic activity from the Earth's crust etc. Tubes especially benefit from isolation from vibration regardless of their origination, especially the small signal tubes in phono amps and line stages, but also the input and driver tubes in power amps. Also digital devices, especially CD/SACD spinners, mechanical "reading" instruments.