There are MUCH more expensive line-conditioners that I'm sure sound even better but these created the darkest quietest background I've heard from other line-conditioners of the same price. I have used MANY Monster Power Line-Conditioners in the past, including the Monster Power Pro 2000, which had either dual- or triple-stage noise-filteration and was $300-$400 new. The only issues I have with them (I say "them" because I bought two "3's" and three "2's") is that they are mainly constructed out of plastic (my Monters were of mostly of metal construction) and only have 7 or 8 outlets (my Monsters of similar pricing tended to have 12-14). Plenty for simpler more modern systems but my home theater uses many separate components and I also continue to use a vintage $1,300 Laserdisc Player and a very high-end at the time $500 Super-VHS VCR. (Yes the picture quality is lacking but I have many obscure unreplaceable VHS tapes and, until Blu-Ray, the sound of the Laserdisc is FAR Superior to compressed movie audiotracks.).