Highly recommend the Blue Circle BC86 Noise Hound. Two are better than one ($110 each).
Those little Audio Prism Quiet Line are OK at $25 each. Minimum of 4, and 8 are better put around the house near noisy refrigerators, etc.
I believe the Richard Gray 400 conditioner is parallel.
The Vansevers 85 and Reference 85 conditioner also uses parallel filtering, so not to limit current.