The amplifier produces more power resulting in more volume. An amplifier with both high-level and low-level inputs provides flexibility by allowing you to build an audio system using virtually any standard factory or aftermarket source unit. High-level (speaker level) inputs accept the signal from the speakers, while low-level (RCA) inputs accept the signal from the pre-amp outputs of the source unit. The ability to boost or attenuate the sub level when an amp and subwoofer are connected to the subwoofer pre-amp output. Switchable input sensitivity gives you the freedom to connect the amp to any standard source unit and have peace of mind it will be within range to properly match the output of the source unit allowing you to use the volume controls on your source unit the way it was designed. Variable bass boost allows you to adjust the low bass within the boost range to just the way you like it. Variable gain control lets you balance the amps output with the speakers or subs the amp is driving. To much gain will lead to distortion and to little will lead to clipping. Variable low-pass filter gives you control over the frequencies that pass through to the subwoofer.