First of all I do want to thank all those who have taken the time and effort to respond with their experiences and what pathways they have chosen.
As we can see there is very little consensus on how to tackle this issue. There is a whole gamut of methods to choose from.
Aside from one or two companies I haven't seen a lot of measurement behind the equipment. And I certainly apologize if I have missed some, I have spent time reading and looking, but I am sure there is bits and pieces of theory and design I have missed.
What I find fascinating is how this whole issue came to light to start with. In the past the SS gear I have owned has never had sonic issues related to isolation, and when using isolation devices the results were inconclusive at best. So my interest in exploring them was quite minimal.
The Classe Omega monoblock amps I use and the Trinov Amethyst never showed these issues when using a pair of JBL 4365 speakers. This only became an issue when I installed a pair of Martin Logan CLX ART speakers. Now it could also be that the subwoofers ended up having increased output from 50 HZ with the JBL to 80 HZ with the CLX. But now this issue has been brought to the light of day.
I ahve been busy on and off today, but I have had time to sit down and listen and the foam material below the preamp/DAC is consistent in its results, and its effects still follow the same pathway. I have removed them to verify its not my internal want for this result, But the effects are consistent and noticeable.
These experiences does point me to the idea that squishy isolation is going to provide the results I need. The Townshend pods look like a viable choice. The EVP pads look intriguing, wish I could get a bit more information on them. A friend of mine swears by the Synergistic Research bullet thingies, and there is an isolation shelf on USAM I believe. But I have a hard time accepting the pathway they work, and that they are a reasonable solution for my issue. However he did bring a set of those bullets once, and they certainly had an audble effect, so I am not able to easily discount them.
Oh as a side note I do use a get o IsoAcoustics Gaia I feet under the Martin Logan CLX ART speakers. The subwoofers do have a set of Auralex isolation bases under them. I remember when I first brought them home, I was dialing them in and had them turned up fairly strong. We have a tri-level house, and our bedroom is upstairs and on the the other end. My wife texts me "what are you doing? Whatever it is stop it you are making me queasy!" The isolation bases broke the coupling with the frame of the house, and she is happy now.
Looking forward to whatever else you choose to share.