TrevC said:
It's amazing how easy it is to imagine differences that simply cannot exist. The OP is a classic example of the placebo effect in action, as are all the WHF reviews of mains products.
I'm willing to believe Placebo may play a part in people hearing improvements to their systems after adding mains products, but when person after person claims an improvement in performance and precisely describes how the sound changed for the better, It's too much evidence to ignore.
People who report increased performance with mains products always(in my experience) state the same findings, including increased bass power and depth and overall increased clarity. If it was placebo, surely there would be more veriety in what way the sound of the system improves as each persons expectations will be different.