Does raising speaker cables off the floor really make a big difference?

Bob
It is doubtful you would benefit much.
I have the same set up of ceramic tile over thick solid slab of concrete and it was opined it probably would not change much.
Again like your self I am very happy with the sound but if it is cheap I will give anything a try.
And I still might on this just out of curiosity.

I performed an experiment a few years back when my system needed to be taken completely
apart and moved to a different room in the house.  I had  an approximate total 300' of speaker
cable running the tri-amped system. I know sounds ridiculous (actually great).  The new location required much less cabling, but being a lazy SOB and doing this in stages I hadn't
cut and soldered ends on the cable, so they remained way too long.  I simply coiled them on the floor, yes bass mids and highs 10 gauge cable makes quite a stack of copper. An audiophile buddy correctly pointed out that  those cables had to be inducing some kinda voltages in each other due to proximity.  I agreed, but I can't hear it. Remember new room new SQ but no apparent problems.  Fat story slim..........I only turned on the bass amps (two ARC mono-blocks) and let some music rip, greater than a kilowatt going to the two woofers.  And guess watt (pun intended) neither the mid or highs made a peep!  I was very amazed.  Not a perfect experiment by any means, but that is watt happened.  Hence I'm not into cable elevators. One last thing (before someone asks) all of the drivers will play the other drivers
freqs.  Tried that as well although at a very low volume. The tweeter will make some "bass"
noises and the woofer will make some tweeter noises. The mid-range is almost full range.

I never argue about tweaks, waste of time.  
 

@dorkwad ,
Before I got the Ikea tea light holders I was using Yoplait Oui glass yogurt jars. The Ikea holders made no difference in sound than the Yoplait jars, but they look much nicer.

Also, I don't think it would make a difference with your tile setup. You can only try it yourself with something cheap for an experiment to see if you would benefit from it, like uberwaltz said.

All the best,
Nonoise

I find marshmallows provide the perfect cushion for the cables