Pioneer GM-ME400X4 is a marine-grade, 4-channel Class D amplifier designed to withstand harsh marine environments and power multiple speakers or subwoofers. Its Class D design provides high efficiency in a compact size. 
Key features
Built for marine use: The circuit boards are coated to protect against corrosion, and the side panels and RCA terminals have protective covers to guard against water and dirt.
High power output: The amplifier can deliver up to 75 watts RMS per channel at 4 ohms, or be bridged to drive up to 300 watts RMS per channel at 2 ohms for subwoofers.
Variable filters: It includes variable high-pass and low-pass filters (40–500 Hz) to allow you to tune the audio frequency to match your speakers and listening preferences.
Flexible connections: It features both speaker-level and preamp-level inputs for connection to a wide range of head units, including factory OEM stereos.
Automatic Signal Sensing and Turn-On: This feature automatically detects an input signal and turns the amplifier on and off, which simplifies installation.
Protection Control System: This system senses the internal temperature and adjusts the input level to prevent circuit shutdown. 
Specifications
RMS Power Output:
75 watts x 4 at 4 ohms
100 watts x 4 at 2 ohms
150 watts x 4 at 1 ohm
300 watts x 2 at 2 ohms (bridged)
Frequency Response: 10–35,000 Hz (Hi-Res certified)