Herbies Pucks floor spike protectors...

My very heavy speakers came with 3 spikes per speaker....the floor is travertine tiles.  Use or not use? (not for floor protection, but for sound improvement)
I’ve used quite a few of his products over the years. He’s easy going and let you know what product to choose. I never use the spikes, even with carpet. He had a product years ago that replaced the speaker feet with a much better non-abrasive concept. I always try and use a wood platform under my speakers with the upgraded feet on that.
You can spend more elsewhere for basically the same concept, but why?
You can't easily get Herbie's products here in the UK so I make do with sorbothane or similar.

However, everything I've read about them seems to make straightforward sense. On a solid floor like yours they may be less effective than say on a suspended floor, but it will still depend largely upon the way your speakers have been constructed. 

I'd say it's well worth a try.   
I use them with my Vandy Treo’s. I use them to protect my wood floors.
I can’t say that they either help or hinder, as I would not put spike marks in my floor.
They also help with moving and adjusting the speaker as they glide easily.
I’d be worried if those spikes could put a chip or make a crack in travertine.
I'd be more concerned with keeping your S/O happy and floor damage.

Years ago, I purchased two dozen of these for less than the cost needed for a pair of speakers.

You might even find something that resembles the Herbies, if you have the patience to wade through the listings.

Speaker/subs,table and CD deck are spiked, so I wasn't about to pay for the audiophool versions.

The description of what the  titanium version is supposed to do, seems a little....
Use Herbie's cone/spike decoupling gliders. They work very well in isolating the speakers so they don't vibrate the floors. I also use them under my rack to isolate from floor borne vibrations. They will also protect your tile.

i have 2 brand new , will save you some money.
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:)
@jtcf ..I remember those days, couldn't afford something and my mind kicked in for a inexpensive work around. Thumbs up.
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. 
 @jtcf bravo !!!! add a nut and you have locking adjustable ! 
I use Herbie's gliders under my Wilson MAXX speakers to be able to move them on a hardwood floor. The use of the gliders did not change the sound at all. If I place my hand on the bottom of the speaker when played loud, I don't feel any vibration whatsoever due to the cabinet material and their weight, so that may be the reason they did not change sound. I really like them and recommend you give them a try; my guess is you won't send them back.
I didn't know Vandersteen made spike shoes.

A quick Google shows they should probably work as good as my Herbie's gliders, though some may disagree.
Some of this stuff can get a bit anal.

I use Herbie’s titanium Cone/Spike Puckies on three sets of speakers. They add a noticeable improvement to the sound quality. Tighter bass with better micro-dynamics. 
In regard to JTCF's post above: I temporally used 8M carriage bolts with my Focal 726-floor standing speakers (two months) while I waited to receive my custom 8M spikes. As soon as I installed the spikes I noticed an immediate improvement with dynamics, sound stage, and bass. I believe you don't know what works until you try it.
I still have some gliders. They didn’t do much for me under equipment rack nor Sound Anchors for my speakers (laminate floor), but they protect the flooring fine :D