Hey rodcad,
I think I recall Auralex bases having been discussed here...May be folks who know did not see your post. If you are not familiar with the forum, in my experience, better results come from using the little search button under the date of the Decware banner. I would try searching Auralex using "all posts" from the time pulldown menu. This may produce some opinions.
Donnie's idea sounds interesting to me. If your try it, and one ball seems pretty good, but not quite, exploring different balls might get you closer to what you want. If you system/room is highly revealing, I think you will hear the differences from various rubbers, foams, woods, and metals used for feet. Perhaps especially, pliable stuff like foam and many "rubbery" feet can be quite different sounding. Very generally, whether rubber, foam, woods or whatever, I am sure there are exceptions, but softer tends to sound softer/smoother/darker. And harder/denser, being more rigid, tends to a clearer sound. It seems to depend a lot on what vibrations the materials are letting through and what they are mitigating....How complete or not is it at dissipating or absorbing vibrations across the frequency range.
I have found that most every foot sounds different, sometimes quite a lot. The realization...No matter the rhetoric, isolation, damping, and combinations thereof, are not the same...some more transparent, others changing the sound depending on how balanced and effective the materials and design are.
I have brick floors, the brick set in sand. Here spikes helped compared to the plinth on the floor, but were not ideal. They were a little rigid and hard sounding. But this is a hard floor and who knows how the same spikes would work on wood or carpet.
Herbie's Small Gliders (mine were adhesive/not screw in) were more refined on my HR-1s, allowing more fine information with more finesse. Enough better to keep at the time, I don't think they were quite transparent across the spectrum...a bit too "warm" and "smoothing " for the sense of broad-spectrum and complex clarity/spaciousness I need. They were pretty good though, and nice to use for fine-tuning speaker placement, sliding pretty easily. I suspect the screw-in models would even be better.
I ended up with threaded Ingress Engineering feet.
http://www.ingress-engineering.ca and they "sound" natural, revealing and balanced to me, on this floor.
They keep going up, an investment for the top feet by now, but presumably better with each iteration's refinements. Below is a variation on that theme that looks interesting to me, especially being tunable:
https://highend-electronics.com/products/alto-extremo-exact?variant=25121381955But these are not in the price range of the Auralex.
Something likely cheaper than those...If you are handy, Archie, a regular on this forum, has made nice platform isolators. It is basically a sandwich of two black painted particle boards cut-to-size to fit whatever he is isolating. There are recesses drilled in each panel to fit springs between the two panels, the springs connecting and separating the boards. The one I use is a really good isolator. If interested, you might PM Archie for more specifics. With your heavy speakers you would likely need some strongish springs, or more of them. I think he has isolated everything in his room with variations of these.
The one I have is under my CSP3. Testing it in comparison with some effective and good sounding "audiophile" feet, it was quite good as-is. But as I recall, there was some remnant resonance I wanted to resolve. Adding damping using some small feet I made was not life-changing, but for me lifted Archie's platform from really good to excellent.
My tuning feet were made with about 1/2" square-cut pieces of Herbie's Audio thick grungebuster material glued in layers with Soundcoat damping material. Just one layer of each is really pretty useful for effective damping refinement...added under the platform, between shelves, or where-ever. For taller feet (say to clear the rubber feet on a component) the right proportions of each material layers really refined mine. For my CSP3, I got satisfied enough with 3 layers of the harder soundcoat, interspersed with 2 layers of more pliant grungebuster material. I like to make mine with one surface, one material, and the other, the other material, as flipping them does create a subtle difference that can be useful. So in this case the "stack" was 2 soundcoat, 1 grungebuster, 1 soundcoat, and 1 grungebuster.
Each of these established damping materials sound different, and I generally don't love either alone. But together they can be relatively balanced and transparent, especially for fine tuning. Putting some of these "feet" under and over Archie's platform made what seems to me to be a pretty world class isolator.
Hope this helps some.
Will