Tbg:
Using my wife's name to respond, but it's me: gbmcleod
I haven't placed speaker cables on the floor in many, many years, not since Enid Lumley said not to (circa 1990). Nor power cords. I've found that precise setup - which includes the room first, the electrical power second, and keeping cords anAd cables off the floor and isolation devices all third, set the stage for everything else to reveal itself. Leaving any one of those three out will dull the results and skew the actual performance of the products in the (usually) wrong direction.
The room is always the first thing I find most poorly addressed. Until the room is out of the equation, a person is wasting money on the wrong things. Of course, if you have a really large room, the room becomes less of an issue, although not a NON-issue.
All those things addressed, I'm sure you're correct. And I agree that
"seldom having the isolation devices in each of the four corners of a component is the best location for them." I'd never found that to be the way to do it. I usually slide the isolation devices all around a location (time-consuming to be sure, but I was the Equipment Manager for Fi Magazine before Harley was, so I do have some expertise in this) to find a "good" position, or I should say the improvement is "good enough." I then move to a second isolation device, slide that around and then to the third. After all 3 are in "good enough" positions (meaning the improvement in a soprano's vocal cords are pretty clear, especially trills), I then go back to the first foot and see if I can improve the clarity (and the transparency). Repeat ad nauseum.
I have no doubt that manufacturer's filters affect the sound, but if they can be turned off, i turn them off when I first get a product, so I can hear it "bare." I use the same logic listening to amps/preamps. First, I listen with the stock cord, and only then do I put in the audiophile-grade cord. It takes much longer, but a person can get a much better system with less money by investing 1), curiosity and 2), time. As Einstein once said, we should never lose our sense of curiosity and awe of 'the mysterious.' I think the same can be said for audio: magic happens much less expensively than most people know: they just don't have the curiosity of "I wonder what happens if I put this...here!!"
NOT investing time costs you a lot more money than investing the time in experimenting.