my 'guess' is the Rossini would end up yielding the greatest benefit. I have mine (TS-150) under my dart pre which includes my phono stages. it is somewhat system dependent based on the amount and proximity of low bass sources in your system.
you can also experiment with 'stacking' gear making sure you block noise pollution from one box to another. I did stack my Playbacks Design digital on top of my dart pre for years both atop the TS-150. I used a Symposium Svelte Shelf between the 2 boxes as a sort of noise reducer.....otherwise my phono stage performance was compromised. it improved both the dart pre and the PD.
ideally the TS series platforms work best on a solid grounded rack on a concrete floor. you want to remove any compliance from whatever it sits on. then it is allowed to decouple the target gear most effectively.
I bought it thinking it would be best to isolate the hard drives in the QNAP, much like isolating a TT, but I see you and others use it for your front end components.
Have you actually tried it under your hard drives?