Listed below are assorted 'tweaks' in descending order of effectiveness - perhaps approaching voodoo.  We moved and have an assorted quantity of each.  $20 per unit plus shipping.

The Alan Maher Designs Quantum Plug-In 2.0 is a conductive-based RFI/EMI parallel filter design.  4 units

"Our philosophy is we don't just treat the last 6 to 12 feet of your home at one centralized location. If you went around your home and counted the many electrical outlets and light switches that are installed, you would have an equal amount of potential noise sources. RF enters the electrical phase through open outlet receptacles, oxidized wiring and contact surfaces, and voltage instability. A typical home has about 150 to 200 potential noise sources, all ringing at the same time throughout the electrical phase. It is virtually impossible to address even 10% of the combined noise at a single centralized filtering location (not to mention the other 90% of potential noise problems). The most effective way to apply filtering in a home should be over distance; it is simpler to suppress noise at various locations around the home instead of trying to focus at one centralized location. Our methodology is to treat the home as one gigantic power conditioner and allow the entire home to reap the benefit of corrected power factor and harmonic filtering.
The QPI 2.0 is our next generation Quantum Plug-In.  The QPI design is one of our oldest and most reliable filter designs, developed in the late 1990’s as a simple parallel filter. As digital components evolved over the years, we expanded our research and development to meet the needs of higher resolution circuitry and power factor correction.

As part of our Smart Grid technology product development, the QPI series is designed to draw zero wattage from the wall and maximize circuit power factor correction.
Our QPI 2.0 is designed for basic universal filtering. The QPI 2.0 is an excellent design to be used with all types of audio and video components.
Warranty: 5 year warranty - The QPI 2.0 is designed to last the lifetime of your home.  We will replace the QPI 2.0 free of charge up to 5 years if the unit wears out."

Dampening plug 2.0 - passive filter reducing noise from switch power supplies and is placed in a socket between your breaker box and the switch power supply.  2 units

STILL FOR SALE

Dampening plug - Moray James Design.  - Same concept.  8 units

The AMD Quadcell Antenna is a different type of noise filter. The Antenna couples to RF and low band EM noise that is floating around your room. The Antenna does nothing to clean the A/C in the wall, but it draws in airborne noise floating around the room and routes the noise to earth (or Neutral in our case).  6 units LEFT,  4/10 sold.

I bought three, one for HiFi, one for office, and one for bedroom because several people with high health sensitivity to RF said it really helped them. It worked well for my HiFi but not for my health symptoms, so I’m selling the two extra. (The biggest help on my health was getting rid of the DECT cordless phones and replacing with Siemens Gigaset with Eco Mode.) Included are plug adapters in order to handle the American plugs. Keep the hole for the Earth pin to the top of the unit.

You only want one QC Antenna for the room; think of it as a star ground to airborne noise. Place 1-3 metres from the HiFi components. Because it routes the noise to neautral/earth, it does help to have some additional treatment for mains noise, which treats neutral and/or earth. From Alan Maher: “You can play with the wall location a little bit when trying to blend with stereo / AV filtering vs. overall Antenna strength interaction. Don't go overboard with close proximity because analogue signals work at different frequency compared to digital signals...and what you don't want to do is a massive suppression because the filter is too close to your turntable which can cause a major suck out ...so if you notice too much top end roll off or suppression just move the Antenna an extra meter or two (up to 3m) from the stereo.”


USB + Antenna - gives a grounding plane for the circuit board of the USB. 

Alan Maker CBF 2.0 - RF absorber (claim) Found no benefit myself.