I am always skeptical of audiophile companies that make big claims for their products but never post any specifications, tests, or even typical graphs of what their components do or how they improve things. These are UK grid units but whatever they do would be applicable to the NA grid, it is just different voltages and mains frequencies.
In your case, your best solution is to either trust them, since you have had luck with them in the past, or not trust them and pass on it. If you do buy them, you can decide if they work suitably for your system.
One thing to remember is if they do make an improvement but they don't justify the cost, at least you have an improvement you can live with. If they don't make an improvement or make things worse, I would send them back for a refund and verify you can do this before you buy them.