Isolation for DAC/Class D Power Amp

... only remaining issue is air borne vibrations from the the music itself.

Not necessarily. How about vibration generated within each device? Some (as me) believe it requires a path for escape.
You may wish to read about this theory and proposed solutions here:

http://starsoundaudio.com/liveVibe.php

(Not affiliated with manufacturer, although I do own and attest to his products.)

isolation on any device helps, now if there was only a way to zero out all rfi in air...............

Many times in the past I have trumpted the benefits of vibration control and the benefits it has reaped and saved me from changing. I am using Bright Star peices for both my CD player and my integrated amp and will never part with them! I have the CD loaded with an Air Mass/ Big Rock and have 2-2 lb. Brass dampers atop it from Eden Sound and for sure as I added peices (starting with the Air Mass, then Big Rock, Then Eden) the differences were jaw dropping for me, so much so that I purchased a Big Rock for the integraged (SS) and heard further improvements. When I first started in digital I realized the differences using Sim Feet but, I now understand better (from hearing) what mirco vibrations due. Now, oh course, this is just my hunble opinion but hearing has made me a very strong beliver.

I found Hyperion Magnetic floaters helpful under my Nuforce Class D amps, but also weighting them down. Many Class D amps are so light-weight in lbs that weighting helps as much with vibration as the isolation.

It really depends on the particular dac or amp. In some cases it helps but not always. Some dacs have a tube output stage so it might be helpful in that case
Alan

I have done extensive experimentation with isolation of my own components, and every piece has benefited.

However, what sounds best under my tubed integrated amp (Final Labs Daruma) may not be what sounds best under yours.

With that said, to answer your question, I'd say your equipment would most likely benefit too, but it will require experimentation on your part to find what works best.

Even for concrete floors structureborne vibration is an issue, trumping airborne vibration. The Earth's crust motion forces the building structure, including cement slab, to move at low frequencies circa 0-20 Hz.