Robs, joining in is there for all
, I wasn't directly having a poke at yourself. If we all agreed about this tuff then it would be a boring place, I just get minorly annoyed with the knockers who just go bollox, fine If you've tried it, if it then does nothing for you cool, but you've tried it.
Leads all types are proberbly the biggest 'black hole' of contension ever, with people quite rightly stating, why should I pay this and that ON top of the purchase price for the Unit, and I do agree. Wadia for example state in the manuals, that their OWN supplied power chord is all you'll ever need to use. 
I would diagree agree whole heartly 
Facts and figures, or validation again fair comment, if figures were published, for various cables, does that mean say cable 'a' with it's lesser amounts of spikes in zone 'b' of the frequency spectrum, will give a more cleaner and detailed sound, or possibly cable 'X' would give a more rounded and fuller bass in the lower spectral registars? who knows? 
Whould you need an industry standard, who would set it, does it work, could it be fudged? (it's all excess B/S)
Some cables work better than others for sure* based on perceptive and imperical evidence, however the only way for you to sure, is a Trial for yourself alone, in your system.
Measurement of a Full frequency spectral sweep, before and after the cable, may prove enlightening, maybe from the wall socket, to the bridge rectifer too. this will give information, but how do you interperate it?, maybe the 'good cables' may produce more rfi in a different region of the spectrum, shifting out the 'way' of that particular companents 'frequency hot spot'
Different cable materials have a different 'sonic charactoristics, different rfi rejection/radiation patterns/could they significantly reduce the size of the radiated field, so this does not effect the surrounding components.
A whole pleathora of therories and suggestion can be banded around here, but for most the bottomline is, does it work or not
.Only the indivdual can answer that. WM