None of us will ever try every conceivable option in a double-blind test covering all possible rooms and systems, so complaining that an honest opinion here is based on partial data seems a tad harsh.
Hydras don’t look impressive, heavy duty or expensive, but I don’t care about that. If pride of ownership considerations lead other people to other solutions, or better hearing does so after extended listening, I see no reason to insult them or their hearing.
I use a Hydra, as do some people I have asked who work in hi-fi shops that are not Grahams. I have also listened to the giggling and sneering from people who have spent decades in recording studios about hi-fi nuts’ fascination with power leads.
After a Hydra ( or equally well-made and star-earthed option) I was strongly advised that the next upgrades to power supply in any normal house and system were:-
Get LP12 or similar non-Naim power supplies as far from the power to Naim boxes as possible and definitely off the Hydra.
Get a dedicated supply with its own Henly and CU all the way from the electricity meter to some good quality sockets for the hi-fi. Earth needs to run to the meter or a ground spike and you need decent cable with appropriate shielding.
I have done both. It seems likely that one can go further, but whether my old ears could detect a difference seems less likely, even with all the other junk between the mains sub-station and my hi-fi.
If someone else’s supply is much more compromised than mine, I can imagine that more complex solutions might bring audible benefits, and the design of (for example) the Sean Jacob’s options looks convincing. However, I have not heard his stuff, never mind doing the extensive multi-ear blind testing required to make statements as firm as some here.
What I can say is that spending money on a dedicated supply can often make sense, and can be great VFM, even if one has a fairly typical mains supply and ‘only’ has (say) ND5XS2 and a Nait. It can cost about the same as one new Powerline…
If someone at that level wants more SQ, and is not hearing hums or clicks when the fridge door has been left open and that sort of thing, I would respectfully suggest that a box upgrade or two would typically give bigger and more reliable improvements. However, if I already had a balanced setup at 500 level, I might investigate sophisticated power options again.
My strongest suggestion if trying above-Hydra power options is try before you buy - and play the ‘improved’ system to 1 or 2 other people. If only you can hear the supposed transformation, it may be made entirely of pixie dust.