If it's a big heavy amp, consider an inexpensive concrete pad as a base load on the floor. These are sold pre-formed at the big box stores. Then use a combo of Wipuna Sound Myrtle Feet on top of 2" x 2" cork/rubber feet under the amp. Caution: Low WAF!
amp platform suggestions...
I was thinking of using some granite with some Herbies Iso-Cup/Lampblack Ball between teh granite and the amps. What are your thoughts?