Surge protection, no filtering, no regen please...

I've been trying a few power conditioner during the last few months, Quintet, Furutech products, APC etc... I found that they all changed the sound... but all of them got worse (limited dynamics or at least something not to my taste).

I know I can't afford a regen like PPP but I want protection.

What's your experience on something that provide surge protection but absolutely does not change the sound a bit?

Thx. Tom.