Filling hollow tubes of my component racks

Custom made to your specs Carbon fiber rods. Use a a fuid silicone teflon lubricant and a mallet to bang it in.
For extra ballast use lead pucks encased in something no one can bight into. To save weight use memory foam torn into pieces, then tamp it down some and place a myrtle wood weight on that. Or potted heavy steel rebar like some waxes or epoxies. Even sound proofing green glue should work but will shrink and need a couple of applications. Just pour it over the metal bars . I guess that potting stuff they put trannies in is good .
BTW anyone know where to get the audiophile epoxy in question? Its exactly the same as the non audiophile self hardening goo,but costs 900% more per unit. You know the R and D burn has to be paid some how. Get the metal shop to make it your own braid and geometry. Use as precious a metal as you can like brass and bronze or damascus steel. This will help justify the obscene cost.
Silicone might feel better if a bit stiff.

The metal that is heavier than lead volume for volume , thus you mean higher specific gravity is ... Tungsten.
It is not cheap but denser than lead. I imagine that an alloy is used because Tungsten is costly.
I am cuurently thinking of making my own version of magnetic levitators strong enough to supporta pre amp. I think the magnet strenth must by definition cause interference and whatever electrical grunge is AKA EMI. but you can get strong neodynium discs easy enough at a price that is not all that much.
I had already planned a needed not just for fun real vibration isloation solution but...
My prepaid never made sandbox is stuck in the hands of it's maker . I hoped to use memory foam from an upholstery shop. I am being very serious here that stuff is incredibly effective. Add some Bear paw footers and you can set the whole rig on the foam . I was hoping to get some 2 inches thick and make a micropure ? tungsten shot? sandwich.