I know I sound like a broken record, but with one exception all dampening and isolating device are springs with some resonant frequency. Some do provide horizontal benefits and others really don't. All this really means is that you choose your poison. Some may like the benefits of a high resonance and others a low one. In my experience everything has an impact on the sound you hear. Racks, feet, and shelves all go into this, as does your flooring. In my old house I had a audio room on the slab of the house--concrete over earth. In my present house I am on the second floor with suspended wood floors. This is a much more difficult circumstance to be in. But even if you are tightly coupled to the earth, it moves and you still have the need to deal with dampening. It is, of course, possible to use multiple materials to have multiple resonance points. I remain unimpressed with these solutions.
I have never, ever, liked soft isolation feet. They rob the sound of all dynamics. I would include in this the majority of wood shelves and racks. Butcher block using maple seems to be the explanation for the few that sound good. The old Tiptoes, especially newer one using special brass seem best. I once had tungsten-carbide tiptoes made to use under my Final Audio, 250 pound turntable. The tips were so sharp that I had to put triple Nickels under them to keep them from penetrating wood or cracking my tile floors. They were great with that turntable.
Long ago I tried Mana stands, having read all their rave reviews. I continue to use them, but I have long since altered their ideas by using shelves on the top layer that are not the plate glass they use. I have found the Neuance shelves are great on the Mana stands, but presently use the Acapella Silencio shelves with their special feet between the component and the shelf. The shelf lies directly on the glass shelf. On this shelf their feet outperform the Roller Blocks, Aurios, Valid Points, and others I have tried.
The exception to all of this that I noted above is the active isolation base by Halcyonics. I have owned two now for several years and wish I could own more. This device has sensors in both horizontal and vertical plains that have voice coils associated with each to vibrate the shelf 180 degree out of phase with any sound sensed by the sensors whether they are internal or external to the device place on top. My oldest unit has leds that shine when a vibration is sensed. You can see when the unit is active in these lights. Especially women's voice aggravate them, although if I walk near the stands, you can see footfalls. Were these Halcyonics to cost $2000 each, they would dominate audio. Their performance eclipses all others, IMHO.
