Imo, it's more placebo. If you believe it affects then you do weird things like cable risers and hanging wires. If you don't believe then you connect your amp and speakers with wires and don't care how they are laid and just enjoy music.
And if you want a low cost and low labour experiment put thermocol packaging that comes with your amp/cdp/dvd player under the cables and see if it really matters .
PS : placebo effect is real but remember its finally a placebo.