What is the Silliest Accessory You Have Ever Seen.

In support of the fuse.  Mijo, You are wrong.  Sure, there are failure modes where the fuse fails to protect the circuit.  But there are many more failure modes where the fuse will save your ass if not also your power transformer.  Power transformers are very expensive and sometimes impossible to replace without engaging the services of a custom transformer winder.  Guess how many of those remain in existence in the USA? Your circuit breakers are probably at least 15A in capacity.  How would your preamplifier look after it passed 15A for long enough to blow the circuit breaker?  Pretty toasty I suspect. I am surprised at you.  And if lightning (not "lightening") were to strike your system, ain't nothing gonna save it.

I haven't tried these so can't comment. But you can DIY with PVC pipes filled with sand on a wood stand. Cheap.

I think a big factor is the directivity of your speakers in mid and high frequencies and how close they are to your side walls. Place near the first reflection point, angled so the three elements present a reflective diffusion the those frequencies...is not so ridiculous.

FWIW, I've seen similar devices prescribed by Rives when they were in biz, and they weren't about selling these but about professionally creating a good listening environment. 

"He has never ridiculed or insulted anyone, but has always shown kindness and understanding."

Never say never.