Quantum Audio Q6004 Amplifier 600 Watt 4 Channel Car Stereo Amp w Crossovers (RPG15) Quantum Audio Q6004 Amplifier 600 Watt 4 Channel Car Stereo Amp w Crossovers Maximum Power 600 Watts 4 Ohm Stereo Stable Variable Input Gain Control Frequency Response 20Hz - 20KHz