Floor standing speaker isolation advice needed.

@cd318, thanks for the reminder. While  choosing my stand solution and height, I have the speakers up on wood frame w/ granite platform amp stands. There were sorbothane ‘half-ball’ pads Gibbon under the granite—bad!
So I replaced with hardwood blocks—much better!
Then one step farther, was raising the speakers off the amp stand surface with 1 & 1/2 inch wood blocks at corners only—even better! Letting the bottom of the M40’s breath freely, like the TonTrager stands achieve, does seem to benefit... so with this finding, your reminders, and geoffkait’s comments on rubber (which is where my concern was), I think I’ll forego the IsoAcoustics Modular stands for these particular speakers. 

@jriggy Yes, you shouldn’t need fancy stands but it definitely a good idea to let all the speaker panels breathe freely. All Harbeths are constructed that way to allow the resonances to fall below the threshold of hearing in terms of frequency range.

The M40s have always been fantastic speakers and are the sum of one man’s attempt at getting as close to neutrality in the midband as possible with the fewest compromises. Does any speaker do voices better?

My best advice to the OP, keeping it cost effective and simple, is not to overwhelm yourself by trying to many things, in to many combinations. Using what you have, first try the individual items you have - by themselves. Listen and compare and if none of the products, by themselves - spikes, sorbothane, granite slabs, etc - brings the sound back to what it was when coupled to the cement with spikes, then try what you have in simple combinations. Usually the simplest solution ends up being the best solution....Jim

Has anyone compared IsoAcoustics Aperta 200 to Gaia (the former being able to accommodate my loudspeakers’ weight/footprint and within my budget)?

I haven’t compared to those but I have some IsoAcoustics Apertas under my KEF LS50 Wireless in my man cave setup. Excellent stands that helped clean things up a bit.

jhills, excellent advice that I’m taking. I have so much stuff already to play around with and if I do spend more, I’ll at least have an idea of what might work best based on materials, application, etc. from experimenting.