I’ve found that cartridges energy often works in tandem with the tonearm. A lot depends on what your prefer. Jonny at Audio Origami, foam fill in his tonearms and the Regas can often neutralise the energy making it a positive or, negative difference. The lighter the cartridge, the better it is.
There are so many combinations available to get the synergy right but the tonearm and cartridge are the least available to demo.
Regardless of wether the Houdini or others work, at least you have the option to try with no risk. Money back guarantee and all that.
With anything else, it’s 14 days but must be returned as delivered. Impossible with a cartridge unless faulty or not as described.
ive never tried the isolators myself but the options are there for people to try. No point slating anything unless you have real experience of the items questioned