Thanks Ozzy, these seem quite affordable and effective, but there is no way to attach them to the bottom of the Cubes, so the Townshend Platforms or Sound Bars are the best alternative.
This comment from the company seems very dubious:
Here is what Stack Audio replied to my question.
"The AUVA Loudspeaker Isolators have a burn in time to let the particles settle. We estimate around 6-7 hours although customers have noted continuous improvement up to the 20-hour mark in the past."
"Just a follow up note – I should also mention that several customers comment that no burn in time is required and there is an immediate impact. I think it varies on a case-to-case basis.
ozzy