I gave up experimenting with mains conditioners 10 years ago, they can do some good things with noisy digital sources but always lost dynamics and overall preferred without. Moving to a well constructed mains supply can provide real benefits but expensive extensions I’m very very doubtful of

If you want a good mains extension use Olson as they are hard wired and use real sockets

if you can install a seperate CU direct from the incoming mains and feed each fuse to a single socket with over spec cable (eg 6 or 10A) this will reduce impedence and provide very worthwhile gains. I’m a big fan of improving mains but it’s more about avoiding weak earthing and high impedence than filtering

A full solution can be affordable – less than £1k all done £600 on an extension is not a wise investment imo

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