Yes the Synergistic Research ECT (Electronic Circuit Transducer) are very effective on pre amps, amps, and front end devices such as DAC's and CD players. My SACD player and amp each have 7 of these small cylinders on them. The nice thing is they are easily removed when it is time to upgrade a device and then use on the next piece of equipment.
In order of upgrade I would do A/C wall receptacle, then main power fuse of each piece of equipment, then ECT, and finally secondary fuses.
In order of upgrade I would do A/C wall receptacle, then main power fuse of each piece of equipment, then ECT, and finally secondary fuses.