Nice thing about speaker wire is that you can experiment and if you do hear a difference then money well spent, but if you don't then just return it. I've always wanted to do a A/B test against the in-wall 20A home wire vs speaker cable... The EE in me says I won't here a difference but perhaps my ears will disagree.
I do think cable isolation is important, I prefer to route power cords separately from interconnects and from speaker wire. Avoid long runs of wire, like to the rear speaker with a cat5e on top. Other than static electricity from carpet, i'm not sure what the concern would be..
