The Wireworld USB cable design is in large part addressing the vulnerability of the data line to be negatively affected by noise present on the power line, when those two conductors are in close proximity. That noise comes from the computer. For super detail oriented power filtering devices, take a look at the SOtM filters made for SATA connections, or even the computer's fan. Those are intended to choke the noise before it ever leaves the computer on the USB line.
I want to try a Wireworld USB cable at some point, but I haven't chosen which one just yet.
Power quality definitely influences the behavior of the clocks. Even in high-end disc spinners or DACs, careful attention to the quality of the local power supply of the clock circuit can make a huge difference between two players using the very same input receiver chip, where one has a poorer implementation than the other. Those clock circuits need power to operate, the cleaner that power is and the more rigidly regulated it is, the better the clock performs.
Clocking involves the use of crystal oscillators, the way they work is a function of the known precise/stable resonant frequency of the crystal (typically quartz). Both EMI and RFI are (invisible to human sight) enemies that pass through and vibrate the crystal in an abnormal fashion, causing jitter.
Borrowed from a German University authored paper presented at the Microwave Symposium Digest in 2010:
The high frequency (HF) crystal oscillator is susceptible to electromagnetic interference (EMI), which affects the stability or accuracy of reference frequency standards. The effect of radiated EMI can be both deterministic and random in nature that shows up as jitter in the time domain and phase noise in the frequency domain.
So not a snake oil type of product in that they are purporting to attenuate EMI by 5 dB, whether that is very/slightly/or not audible with any given DAC is of course open to each individual's personal take.
I'd be curious if you have a try and buy scenario available with the iPurifier, what you think, especially with loudspeakers where the stereo image is greatly enhanced, to me the single biggest difference. The sound stage becomes both larger and more precisely focused when used with the Herus, and that is a function of a blacker quieter background.
Please post your findings if you get a chance to audition the iPurifier with the Herus. It won't take the form of "brilliant with/sucks without", however in my experience there is a noticeable improvement.