If by "clean power" you're mainly concerned that your sound quality isn't diminished by imperfections in the power coming out of the wall socket, your audio equipment already "cleans" it. The power supply sections have transformers, rectifiers and filter capacitors which process the AC coming in and furnish clean DC for use. There's no need to spend money on an external unit to do this.
If, on the other hand, the primary concern is possible damage to equipment caused by lightning, etc., as has already been mentioned, the installation of a whole house surge protection system can be effective against events which the equipment can't handle routinely. Separate individual units don't have similar protective ability.
