I think the vibration rationale for improved sound when using coasters is laughable The only people saying they hear a difference are those marketing the product.
Yes you need to isolate a turntable obviously. components come with special feet that offer isolation as they should.
And amplifiers certainly don't need isolation as they are built like a tank and quite heavy.
Maybe if you live on top of the subway platform or a raging Street prone with lots of noise but then why bother if this happens.