Is it better to isolate the plinth or the amp?

Both try SYMPOSIUM!!
Thank you for your replies. Just ordered MapleShades Vibration 2 kit.I have an inclosed audio cabinet w/glass doors. I installed a roll out shelves made of mdf,I'm going to put a sheet of iso pad they sell for HVAC installs in between the mdf & 1 5/8 granite slab. Any suggestions on what height in between the granite & the Mapleshade? My amps are going to sit on the Bearclaw Sr.s All suggestions are welcome. AMB Dan M.