Rockford Fosgate M400-4D 400W 4-Channel Full-Range Class-D Amplifier + Amp Kit New Rockford Fosgate M400 4D 400 Watt 4 Channel Full Range Class D Amplifier Amp RMS Power Rating: 4 ohms: 75 watts x 4 chan. 2 ohms: 100 watts x 4 chan. Bridged, 4 ohms: 200 watts x 2 chan.