Isolation Devices

I would have never believed what the difference in sound a simple isolation device can make unless I actually heard the differences myself. I have a hardwood floor in my listening room and after adding Isopods under my spiked Thiels (MDF sandwiched between) the difference in detail, presence, and bass was very satisfying. I thought that the next tweak would be to add Isopods to my Cal Alpha DAC. I replaced a bicycle inner tube under a piece of MDF with Isopods. After days of listening, I tried to convince myself that my sound had improved but my ears told me a different story. The Isopods made my music sound hard and edgy. I replaced the Isopods and went back to the old bicycle inner tube and the sweet warms music returned to my system. I am confident that I used the correct Isopod models for my DAC. I'm looking for Isolation devices to impove all componets in my system. Is it overkill to isolate a power conditioner, transport or preamp? Any other devices or tweaks, do-it-yourself or manufactured? dh