Here’s my take on things and (I’m not going to argue about the EtherREGEN - I’ve said all I have to say based on published objective measurements of that device)
I had what I believed to be a fairly well sorted system - very neutral, transparent, cleanly measuring source and amplification (>110dB signal over noise and distortion), well designed speakers - low resonance cabinets, benign impedance and phase, very low distortion drivers and high quality crossover components, plus >£1000 worth of room treatment (diffusion/absorption mainly around the listening area). I recently got hold of a Focusrite Scarlett 2i2 and a calibrated measurement microphone, downloaded a copy of REW and properly set about meauring and correcting the room response.
To be fair, I was quite surprised that the room measured fairly well to start with, but there were a few peaks and dips in the bass and a general loss of energy at higher freqencies (no doubt due to the effects of the diffusers/absorbers):
Left channel in red, right channel in green
After 3 sweeps per channel (~120 averages per sweep), then averaging the sweeps into one left and one right response, applying auto EQ and then tinkering with manual EQ to flatten things out a bit more:
The response is now +/- 1.5 dB from 40Hz to 18.8kHz (my hearing runs out at ~16kHz)
I’m now listening to what is, by far, the best sounding hi-fi system I’ve ever heard. A couple of hundred pounds worth of equipment including the cable and connectors to make the input/output and loopback cables and a day or so of my time is all it took to elevate my listening experience from pretty darned good to absolutely sublime.
Forget emptying your pockets/wallet on endless tweaks. Spend some time and money on your room - the benefits are orders of magnitude greater than the meagre investment.
Once you’ve sorted your room, if you want to go nuts splashing cash on placebo, knock yourself out!
People talk about noise over ethernet being the reason they can hear differences in sighted listening sessions, but I’m not buyinig it. Objective measurements show no improvements in noise floor with our without the EtherREGEN and other tweakery such as audiophile network cables, switches etc. And John Swenson himself has still, to date, not come up with any measurements to back his claims of improvements in the analogue domain from using the EtherREGEN.
I’m staying out of these types of discussions in future. They always circle around the same arguments and they are a fruitless waste of time and energy.