Where to use Isolation devices

Some good responses, thanks. The latest isolation device I was able to try recently was the Nordost Sort Kones. The shop I went to said that he would be money on the fact that I could hear the difference between a cd player without anything, and then with the Sort Kones....well he was right. I heard a lot of difference with the Sort Kones in regards to inner detail, more decay with the cymbals and drums, and I guess a little more air around everything. They are cheap at 60$...I am going to get three for my cd player to start out with.

Sean34, the Sort Kones are actually a coupling device that is in fact the opposite of an isolation device. The coupling devices, in theory, provide a path for any vibration to leave the equipment while isolation devices should isolate the component from the surrounding environment. Having said that, they are used for the same purpose. I have three sort kones and believe that I hear a difference as well.

I wish I had two identical CD players that I could setup identically for an A/B test that didn't involve the delay of installing and removing them.

I think an idea setup just might be a chunk of marble or other heavy inert platform that is sitting on isolation devices with the component on coupling devices on top. Should be the best of both worlds, in theory.

I agree, it appears that the right combination of coupling and de-coupling devices gives the best result.
I am going to try this approach with speakers as well, that's spiked speakers with Boston Audio tuneblocks for speakers under them.

I tried herbies rubber cup and black ball footers under my Modright Sony 5400ES and did not like the results. I then placed black diamond racing cones into each of the herbies cups and wow this improved the SACD player ten fold. It got rid of the slight brightness of the black diamond cones yet kept the detail. I placed the herbies balls by themselves under the separate tube regulated power supply and am pleased with it.

Thanks Mceljo for the clarification. When I heard the Sort Kones, they were under a very high end Meridian cd player and the top of the line JM Lab Utopia's with some sort of expensive SS monoblocks. There was a lot of resolution and detail, so it was pretty easy to identify the difference.