Would sand help my amp?

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.

Ventilation and heat dissipation might be compromised. If the sand had any conductive ingredients it might cause a short or worse. The sand could have corrosive ingredients. The friction might cause cosmetic damage which would compromise resale value. Could attract pets. Might be messy.
Small fireproof/sealed bags of sand carefully placed might be worth trying.

I doubt that burying your amps in sand will do anything positive and will almost certainly have long-term negative effects. If you are concerned about the housing of your amp vibrating, or responding harmonically to soundwaves, then you might try the VPI "Magic Brick", which was "invented" to address exactly these problems.

Brightstar Big Rock sand box is what you need. Yes they work for amplifiers also.

Tizzines usually has more to do with power, power cords, speaker cables, or interconnects.

For "tiziness" address line conditioning, upgrade AC cords, & cabling compatibility issues. However, distortion only at high levels is probably just simply amplifier output-clipping, where the unit is running out of gas.
Insulating an amp in any type of sand, mud, whatever material, is begging for heat related failure. Heat sinks aren't made for their appearance, they actually perform a critical function. And if tubes are in the mix then you're really asking for trouble.

Hi RL, I think you would be very disappointed with the results. It might make for a very dull sounding system. I am a huge believer in some of the better audio racks and platforms. I have come to the opinion that a good rack/shelf is as important as any audio component. I am not talking from some deserted lsland. I have heard many materials, too many to name. I have heard a few (and a few not so good)rack/shelves devices that are capable of transforming an enjoyable system to one that is more of an experience or the illusion of what gets you closer to the music. Some of these rack/shelves will give you the full potential of what your gear is capable of. All the posts above have given good advice. Dedicated lines in some case can be very cost effective. Don't need to to go out and spend a bundle. One piece at a time should not break the bank. Also, it may not be the amp causing the "tizziness". If possible, try moving your speakers around. Try some kind of cushioning in the corners of your ceiling. If possible try Neuance with a rack that Ken from Neuance will help you with. Try Sistrum products. You will not go wrong with either. Hope you find the life, energy, light that these products and tweaks have done for me.