Amplifiers
At the centre of your Hi-Fi system is the Amplifier. The amplifier outputs the audio from your other devices through to the speakers and lets you switch between each of your audio devices. An amplifier can control Equalization, Pan and other audio settings.
A good quality amp can really make a difference, and the sound produced by a separate amplifier is easily superior and more powerful compared to most all all-in-one Hi-fi systems.