I think a lot of this talk about isolation goes way beyond what's necessary for great audio enjoyment. As my equipment got better (and much heavier), the footers I used had the opposite results: muddier sound.
Taking them out and placing them directly on a thick, maple shelf, pretty much does the trick. I don't have the room, vertically, to try out anything new so I went for some constrained layer damping pads from Les Davis Audio and heard a very slight improvement. That confirmed my suspicions, for now, that the way I have it now is quite good.
Any well made piece of kit has, at the very least, some vibration isolation factored into its design. Yes, you can go with an all out assault on your setup and eventually find something that betters your situation, but you're chasing some very diminishing returns with your wallet.
Even my JBL speakers use small, wool felt dots between it and the metal stands that tilt them back a few degrees and the whole thing rest on a carpet, over concrete, over wood. The stands are flat with no spikes or footers of any kind and the imaging is rock solid.
All the best,
Nonoise