It's rather rare for speaker level cables to pick up severe RF interference. Before you do anything else, I would swap the speaker connections to another location (front speaker outs, possibly) and make certain the problem exists in the cabling and not somewhere else in the system. If the noise abates when the speakers are driven from another speaker output, connect other speakers (fronts) to the surround outputs and check for RF pickup with a shorter run of cable.

You haven't said whether this problem just began or has been developing over a period of time or has been there since you connected the system. You might find some relief by simply doing a basic housekeeping/cleanup on your system and using some Pro Gold on the jacks and plugs.