The amount of continuous power, measured in watts, that an amplifier produces is called RMS power. The higher the RMS figure, the louder and cleaner your music sounds.
Some amps include circuitry that allows you to boost the bass output, ranging from a knob or button that provides a set amount of boost, to a built-in parametric equalizer with many possible configurations and adjustments.
Preamp outputs are RCA outputs that let you pass the preamp audio signal from one amp to additional amplifiers.
Useful if you're adding an amp to a factory radio, or don't have enough preamp outputs on your aftermarket receiver. Speaker Level Input Types: Harness, Speaker Terminal, RCA.