To try stopping it.. try spreading your speaker wires apart and away from power sources. The more bunched up and closer they are to other cables carrying power, the greater the pickup of the radio signals or whatever type of signal. When mine did that, I had to spread my wires apart and move the subwoofer around too. Also try turning the power on your subwoofer down if you can, they carry a lot of juice. Also just play with it a little, when i moved my sub around the floor, it would pick up signals in certain areas and move it a couple of inches then i got nothing. Hope this helps.
If all else fails, buy some speakers that are shielded and get some quality speaker cables, I'm sure you can find a hot deal..... I see your name on the hot deals forum all the time.