Yes I have two APC H15 which are 1500 watt power conditioner/voltage regulator/surge protection capable. I don't count on the power conditioning features of these devices to make audio or video any better but they are superb protection from lightning which is a frequent guest here in South Florida.

I would not expect the hissing to go away by plugging into a power conditioner. Most audio equipment conditions the power using the built in power supply. It is likely caused by something other than the receptacle power supply. Try using a different outlet or a different circuit. Is it a hiss that gets louder when you turn the volume up or does it just seem to go away due to higher SPL. Does it do it on all sources or only a specific source. If it is more of a hum than a hiss then it is probably a ground loop hum and could be due to your cable or satellite hookup. Check all your speaker connections to make sure you haven't got a strand of wire touching anything other than the lugs. It could be induced by close proximity to an RF source.