Assuming you're talking a solid state amp, the problem I'd see here is heat dissipation, whether via external or internal heatsinks; you might melt all your circuitry. I'll leave it to the more qualified persons to comment. If you put the thing on top of a sandbox, and damped the top with a bag of sand, you might get most of the effect you're looking for. This isn't too far-fetched; I'm currently having external passive crossovers built for my satellite speakers to take the crossover circuitry out of the speaker enclosure, and one of the things being considered is filling that crossover box with a very fine sand to damp internal resonances. In that case we may not be dealing with much heat dissipation, so it may be doable.
Would sand help my amp?
Seeing a recent thread on sand-filled speaker wires got me to thinking. Would burying my amplifier in a tub of sand reduce or eliminate any potential harmonic disturbances? I don't *think* that the sand would do anything to hurt the amp (power amp, no moving parts), and it just might clean up this slight tizziness I hear at high volumes. What do you A'goners think? Has anybody tried anything like this?