I have a DIY platform and some isolation materials below my monos (inner tube, concrete, roller bearings) and really like the effect of the combined setup. The platform alone was clearly inferior to floating the amps in air and roller bearings. It's not a huge difference, but if you want the most out of the support structure under your amps, you'll have to go beyond a simple rigid platform.
I'm sure if you start with a good platform, these additional tweaks will work even better.
Peter