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

You will need a footer that will pierce the carpet and couple the speakers to the concrete floor. I like Stillpoints, but if you need additional height, Eden Sound and Mapleshade make robust and tall brass spikes.

I use Edensound bearpaws under my speakers and turntable very happy with the results.

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