they condition the power, thereby improving sound and picture.
They don't improve picture or sound quality, they won't make better toast or a better vacuum either.
There are no standards for measuring power conditioning,
There are many well respected standards for measuring the parameters of a power supply.
There is no agreed upon definition of "power conditioner"....what could a power conditioner possibly do to the incoming sine wave to make it 'better'?
The Acoustic Research unit has a network hub
A hub? Does anyone actually use hubs these days when a switch is cheaper?
which conditioner would you recommend?
The only 'conditioner' I've ever seen, that wasn't just a bunch of low quality L/C Pi filters, was a motor driven variac, voltage stabilizer, feeding two 25KV, 4Amp DC supplies for a TV transmitter....You don't want that in your home though.