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

You are basically saying you bought new speakers, but you do not believe Vivid Audio knows what they are doing. Spikes will in fact alter the tonal balance. That is what changes the way a speaker images. It is no secret, manufacturers of stereo equipment have been playing this game for years. It used to be desirable to maintain as much warmth as possible and still have good imaging, but the scale is swinging the other way with imaging heading the list of priorities. The question of the day is how vivid is your system and how well does it image? This is why we have audiophiles who listen to live unamplified music and say their stereo sounds better.
It might be a good idea to contact Vivid Audio regarding your concrete floor. They may have some suggestions for you.

When you contact Vivid, ask them at what height they expect your ears to be, and then tell them what height your ears actually are.

Chuck

Mapleshade brass cones customized to replace your spikes.

I can't say that I've experimented with all the brands that you've mentioned, but I was very impressed with the sound of Audio Points by Star Sound Technologies. Specifically the 1.5 AP-A's.

Have a look or let's say listen to where and what you sit on. Rise or lower your head/ear position. A good stable listening position is often over looked. Also try adjusting the spikes to fit your preferred listening position. Lower in the front spikes and rise the rear ones. Location, Location, Location.