Hi Keith,yes the most benifit is under the centre speaker where i use three Russ andrews small oak cone feet.My floor is concrete so the mains are spiked. Howerever i do use three small cones under my cd player where they affect subtle changes in the sound which subjectivly i prefer.
Was - sap? I would say this thread needs to look at the root cause of isolation problems. Any decent hifi branch can also help to stop you going completely conkers!