MDF Rack dampening question

Hello all,
I'm using a 4 shelf MDF rack that has hollow alum metal columns, and plastic looking (may be silicone) footers. Floor is porcelain tile. There's lots of empty space between the shelves.

I feel vibration on my equipment while listening to music and I'm wondering if there is anything I can do to help eliminate this (short of replacing the rack)

Some ideas I am kicking around are listed, wondering if you have tried and if it made any difference.

Fill hollow metal columns with sand
Changing footers to brass spikes
Dampening material under each shelf (Dynamat Extreme or another) which would also block EMF between shelves
Mounting each piece of equipment on butcher block w vibrapods (or similar)

I filled the vertical tubular columns with sand. They used to ding like a bell when tapped, now it's a thud.

The shelves are relatively thin, and transmit vibrations easily. I'm going to try some dampening sheets under each (Dynamat Extreme)

How can I tell if the shelves are MDF or particle board? They're completely painted smooth flat black. How does that make a difference in my strategy?

I see many put their equipment on top of butcher block or other thick wood platforms with some isolators (cones, etc.)

StudioTech hf-4

Just looked at the specs, says its medium density fiber board.

Wondering how much a low end rack is really affecting the sound..
Home Depot "natural play sand" They had another, much thinner, called leveling sand, but I was afraid of the mess.

Ordered Dynamat Extreme 10435 door kit ($50). Trying to increase the mass on each shelf to reduce vibrations, and also it should give some EMF shielding between components because it has an aluminum sheet.

We'll see what happens.