My experience with the external devices is that they are not as effective. What I disvcovered is that the whole dedicated line must be treated BEFORE the wall sockets. I got this tip from one of the engineers at ES. Going this route is a lot of trouble, and people in apartments realy cannot rewire their sound rooms. In additon, once the power cord leaves the outlet, some ferrite cores help minimize internal RFI. Most amplifiers put back a certain amount of it, whihc is why the front ends should have their own dedicated power line. Using a good quality power cable is still good sense, but forget those $3000 fat worms and hire an electrician for one tenth the cost.