So......what do you use under your speakers?

I found that floors are not square, and one speaker may be off just a hair...just enough to blur the sound. I use a laser to find the exact pitch of each speaker, and then shim if necessary.

Thanks for all the recommendations. Let me say the problem isn't with the speakers. In fact of the many 30k plus speakers I have had in my system these are by far the most musical, natural, versatile ones I have owned/heard. Since they are new I have had brass floor protectors glued onto those teflon furniture mover discs to make it easier to move them around in order to find their sweet spot. After experimenting I realize that I prefer the speakers about an inch or more higher than what the stock spikes will give me. I also do not like the sound of the spikes in contact with my cement slab. I did speak with Stillpoints and their sales mgr. said that the Vivid G2 speakers are among the few speakers that would not benefit from their products, which he said was a testament to the design and build of these beauties. So at the end of the day what I would like to acquire is a product the will give me the height requirements I am looking for and that will serve to isolate the spikes from my cement slab without altering any frequency range but that will enhance the speed, articulation, etc. of an already SOTA speaker system.

Large Tupperware boxes filled to the brim with beach sand. I was warned by a speaker maker not to use this with his speakers. So, of course, I tried it out -- excellent.

Like you, Nobrainer, I have a concrete floor covered with commercial carpet and no padding. A couple of years ago, I bought speakers with plinth bases (no spikes). Since my floor is not flat, the speakers wobbled. I tried using shims and pads to level and stabilize them, but I was not totally susccessful. In the end, I reached out to Sound Anchors. For $325 shipped, in about four weeks, they made me custom sized cradle bases with three-point adjustable spikes. The bases are solid metal and heavy, and fit my speakers perfectly. I noticed, after installing them, the very sort of improvements you are looking for: Cleaner transients, more stable images, and a slight increase in clarity. A great value.

I replaced the stock screw-in feet on my speakers with the Grand Prix Audio Apex footers. They're a blend of carbon fiber and some sort of polymer/sorbothane, as I recall. Pricey but very effective, and allow for leveling.