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)

Im not sure I understand. Am I going to get negative results by adding mass to the rack with sand in the steel tubes and dynamat to the shelves? Floor is concrete, sub is on vibrapods, so I believe most vibration felt on the shelf is via the sound waves over the air. Other than getting the shelves made out of birch or another material, what else can I do?
I just bought the Studiotech PS-3 with the optional high mass cone feet for my TV/tube system. It replaced a flimsy rack with glass shelving that was clearly not made for audio at all.

The HF-4 is similar but I went with the PS-3 because of the added bracing. Its very rigid and with the cone feet on my carpeted floor and a 80lb plasma on the top shelf it doesnt move at all. I can tell you it is a huge improvement sonically - the bass is tighter with more separation, the mids became more lush and the highs seem to have smoothed out a bit too. Now certainly, this isnt a high end rack, but it was a very noticable improvement in my system for not much money.

I have my CDP and tube preamp sitting on the middle shelf and my Power Plant Premier sitting on the bottom shelf. My amps sit on Timbernation maple stands with brass cones to each side of the rack. Im ordering up some Black Diamond Racing cones for further isolation on the 3 rack components but so far Im happy with it.
Adding mass is not all bad. Choosing the right material for that added mass is different than what we all were LEAD to believe. Mixing and matching materials and geometry is like trying to eat a soup sandwich. If the brass is doing such a good job as a conductor why use rubber products or carbon fiber? Why jumble up the phase coherency and transfer speed by using dissimular material and geometry? Transfer methods are the opposite of damping/storage methods.

Alex you need to ground that rack first to the floor. Audiopoints are what I would recommend and the only coupling device I use and sell. What size, well call Robert at Starsound. Whatever size fits then also use the APCD coupling discs under each Audiopoint for surface protection as well as an increase in surface tension, resonance capture and release. As your budget progresses apply the same ideas and methods to the components shown on the rack ..and also your speakers. Resonance transfer is the method of my choice such thing as isolation. One method one singular coherent voice.
Installed Dynamat Extreme under each shelf, took about 20 minutes total. Shelves feel much more solid now, and has definitely reduced vibrations for each piece of equipment.

Problem is at the same time I upgraded the power amp to a McIntosh mc7200, and upgraded the Oppo 980 by bypassing the opamps with better caps, and installing cardas RCA connectors.

Does the system sound better? Yes. How did the rack dampening with the sand and dynamat make a difference to the sound? I have no idea.
Instead of messing around with your rack to dampen vibration, you instead might want to try using the Herbies Audio Lab Component Top Weights to lessen the vibration. I put two of his Super Sonic Srabilizer(s) on top of my pre-pro. Without them, when I tapped on the chassic I could feel vibration. With them, the vibration was gone. They cost only $20.00 each so you won't break the bank.