Does raising speaker cables off the floor really make a big difference?

It will make a difference to the look of your room, but not to the sound of your hifi.

If the same degree of sensitivity that some people claim in their hearing prowess was declared in the other senses the individual would certainly be considered a candidate for psychiatric evaluation.  I don't think I've ever heard anybody claim to be able to see more clearly by elevating their lamp cord.  Or that the heating pad on their sore back emitted a better quality heat by rerouting the power cord.  Only in audiophilia does this psychosis exist.