Herbies Pucks floor spike protectors...

I added the Decoupling Gliders in brass a few months back to ride under the 3 spikes per speaker.  I felt that they brought a nice touch fullness in the lower registers without losing musical definition, and the mids up seem a bit clearer, too.  And they make moving my speakers a breeze, so for the money they are a great addition to my TAD CR-1's (which like getting more fullness down there).

I am curious to try the IsoAcoustic's Gaia's for comparison to see if they take these musical qualities further.

as I recall OP has 5a. I have used the Vandersteen spike shoes with five A, 7’s and the amps which are also spiked on both tile and hardwood to good effect. they are machined w felt and fit your cones, reasonable for made in USa, available thru your Vandersteen dealer

You guys will laugh,but I have little carriage bolts from the hardware store screwed in instead of spikes with felt pads on the bottom.Cheapo adjustable gliders:)

Several good suggestions made by all above. Take a look at all the products for speakers made by IsoAcoustic's in order to get a feel for other ideas.