I really don't believe there is a conditioning device out there that doesn't limit current to some degree. I would certainly like to hear it, if such a thing exists. Having said that, conditioners are fine on front end components. Forget about them for amps, tried way too many, sick of trying.
As for choices, who can say, everyone has an opinion. You will have to try a wide variety to get to your personal choice. Personally, I like my BPT 3.5 Signature.