What isolation feet under your amp with great result?

OP, suggest you research the following:

Barry Diament 
Ingress Engineering 
Townshend
Symposium
Stacore
Taiko
Machina Dynamica

For a diy solution read Barry Diament, buy Ingress cup/rollers combine with a slate or granite platform and a spring like Machina Dynamica or inner tube.

Other makes are ready made solutions that work.

Avoid rubber.