I have not been following this thread but re. power-line filters in general:
- Current demands for power amplifiers can be quite broadband and rather large. The transformer in a conventional supply will limit it somewhat but SMPS can place higher-bandwidth current demands on the line.
- Inductors exhibit hysteresis (asymmetric response) and when significantly over-driven (too much current) can themselves exhibit large voltage and current excursions (spikes, glitches) with pretty nasty waveforms that generate a lot of noise. Transformers are also inductors, natch.
- DC resistance (DCR) will add voltage (IR) drop on the power line so high-current lines require low-DCR inductors.
- It is typical in my world to select inductors rated 2x or more the peak dynamic current expected in the circuit.
- Many cheap power-line filters in power strips are marginal at best for high-power amplifiers. Charging the power supply (decoupling) capacitors can require fast, high-current pulses well above what the power output to the speakers may indicate.
- As an aside, many cheap strips (and expensive ones) use metal-oxide varistors (MOVs) to limit voltage spikes. These have limited ability to handle spikes and limited lifetime. I'd bet there are a lot of 5-10 year old power strips with bad MOVs. Even the working ones often have a very high let-through voltage; years ago I measured a cheap strip and it would allow short spikes of ~3 kV to pass. A good strip was <1 kV (industrial unit rated at 600 V let-through; note a 120 Vrms wall outlet is about 339 Vpp).
I generally don't use line filters on my power amps, and am of the opinion that decent electronics have such high power-supply isolation that they are not needed on low-level components, either. My area is subject to fairly frequent power outages so I do use UPS units on most of my more expensive and critical electronics such as computers and A/V equipment. I also have a "pure-sine" (expensive) UPS on my aquarium to keep the filter and air pumps going -- motors can overheat with inexpensive UPS units having very coarse (high-distortion) output.
IME/IMO -- I am not a power expert. - Don