You should also consider using Vibrapods as the interior isolator. They're cheap and when used in multiples can support heavy weight loads.
"sandwich" platform for amps
I want ot build a "sandwich" platform for my monoblock amps. I undrstand a "sandwich" approach is best, that is, maybe 3" of acoustic foam layered between either mdf or maple wood shelves. Where dos one buy acoustic foam, and what kind is best; I know it must be very dense. Thanks, larry