Well I did it...I ordered a 20-40kg set, which arrived last week for my power amp (SAC Glowmaster KT88) but they didn't impress me greatly over the stock rubber feet. I'm sure there was probably a slight improvement but if it was there it was really rather too subtle for these ears.
But the story continues...I also ordered another 2 sets of 5-10kg types which arrived yesterday. They were to go under my pre (Audio Experience A2 SE) and my DAC (Chord DAC 64 Mk2)and the difference they have made is in a word staggering. Of course how they perform will be system and room dependent but in my setup the improvement is significant. I no longer get that hardening of the upper frequencies when I turn the wick up, the soundstage is tighter, less diffuse and it has taken a couple of steps outwards in all directions. I thought my system was already quite revealing but I am now hearing further into the mix. (The Spike Sound Wills replaced my Seismic Sinks under the DAC & Pre, I am still using the SAP Relaxa 1 under the transport).
For the money these things [in the right application] are brilliant and even if they cost twice what they do, you could probably still describe them as value for money if not cheap. I'd recommend you audition these in your systems and if you can get them on a months trial it really is a no-brainer. Admittedly they didn't impress under my power amp but I'm intrigued now to see if what effect they'll have under my speakers so I may end up ordering another set of 20-40kg anyway as I fall deeper into the rabbit hole!
Just for the record, I have no affiliation with any audio distributors, manufacturers etc. This is just my penneth worth, both literally and figuratively.