Loading speaker stands with?

Well the poly foam sounds like something the Harbeth guy would suggest.

Stands are really helped by weight. Or at least that used to be the logic. 

Foam Packing will deaden a ring that occurs when striking metal. 

Particle Fillers are a design to control amplitude transferal, each Particle needs to take on amplitude and transfer this energy across all Particles. The physics is that the energy is becoming a conversion to heat rather than a amplitude being efficiently transferred. 

A additional Footer under the Stands does also work wonders. The amplitude ftom ambient amplitude is reduced, hence, the Speaker Stands are not being directly impacted on. 

My experience is Suspension Footers work great, and there are now available 3D Printer suspension footers, that are inexpensive and may prove ideal for long term use. The iitems will certainly supply a god impression of what a much more expensive option can deliver. 

It all depends on your standmounts and the stands.  I did a lot of research on this topic too.  I went with Monolith stands that are very heavy and sturdy.  They are metal and wood with heavy spikes which worked for my thick carpeting and under padding. I mounted my standmounts with 3M mounting strips which Velcro together.  I kept the protective film on the bottom of the speaker to attach the adhesive strip.  They are secure and there’s no resonance playing at even higher volumes.  No vibrations or ringing.  I cross them over to subs at 80 Hz so there is no low level output which might cause vibrations.  Bottom line is I didn’t need to fill the two hollow metal tubes on each stand.  If I was going to fill them I would have used  aquarium rocks which have no scent.  I wouldn’t put more metal in metal tubes so steel shot was out and lead is too dangerous.  Sand can be messy.  Good luck in your new home and Let us know what you decide to do.  

https://www.google.com/search?q=3D+Printer+Isolation+Footers&rlz=1C1GCEA_enGB1190GB1190&oq=3D+Printer+Isolation+Footers&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIICAEQABgWGB4yCAgCEAAYFhgeMggIAxAAGBYYHjINCAQQABiGAxiABBiKBTINCAUQABiGAxiABBiKBTIHCAYQABjvBTIHCAcQABjvBTIKCAgQABiABBiiBDIHCAkQABjvBdIBCjE1NTI1ajBqMTWoAgiwAgHxBd2n8bvsYhgU&sourceid=chrome&ie=UTF-8

I’ve had lead shot and fine sand filling my stands for 20 years and have recently done some other speakers with the same lead/sand mix... the idea that lead is toxic in stands is ridiculous, your not eating it, your not handling it, it’s inside your stands never to be seen or hurt you. 

If you’re extra soy you can wear some gloves when filling your stands, but nothing will happen to you and it’s the heaviest and best thing that you can use, and not too expensive although it’s way more money these days.