Brave man, McGowan...

Brave for sure. This will alienate a bunch of people. All cable haters and snake oilers. Very risky business for Paul to post this in public forum. 
I listened to a pair of Vandy VLR's powered by the Belles integrated using a Bluesound Node as source.
At first the VLR's were using a lower grade AQ cable (GO-4). When we switched to the William Tell. It was quite obvious that the Vandy's were performing at a significantly higher level.-And, this is without a subwoofer.
In fact, the new cables enabled the VLR's to reproduce bass almost equivalent to when they had the subs connected.
A truly mind boggling event.
Now, would I spend that much on speaker cables for a pair of bookshelf speakers?
Probably not, unless I heard the difference in performance.

Though it might be more rational to buy a higher quality amp and use an off the rack power cord, I think my audition shows that cabling even 2nd tier equipment with high quality power/interconnect/ speaker cables can make a huge difference.
Nothing matters ———-/——-> Everything matters

find where on the continuum you achieve happiness 

Power cables can make a big difference. Any cable can make a difference. The difference might not always be an improvement or the difference might not be worth the extra $$$ you might have to pay.