steven0713,
First of all, the quote from Richard Vandersteen is absolutely correct. This is my experience. I went from 15' to 8' of the same Rocket 88 speaker cable and found a slight, but noticeable difference in details against a black background. Psychoacoustics? Possibly... But the real change came from replacing Rocket 88 and moving up to William Tell ZERO in 8' length. That opened everything up, considerably. eagleeye7 describes it exactly correct, just above.
It's an expensive upgrade, but if you are placing plenty of your money into mono block amplifiers than don't stop there. Feed them the signal that will yield the best results. This also includes high quality power cables, if you don't already have them. Note; William Tell ZERO is a full-range speaker cable. If you are running bi-wire than you would need to buy the bi-wire combo setup. It's very expensive. I went with the full-range William Tell ZERO after coming from my bi-wire Rocket 88. Man, it is awesome!
Best to you.