Amazon.com: BLAUPUNKT AMP1404 1500 Watts Maximum Output Power 4-Channel Full Range Car Audio Amplifier + AUDIOBANK 6.5 Coaxial Car Audio Speakers 400 Watts Peak Power - (4 Speakers) : Electronics
2 Channel Amp vs. 4 Channel Amp
Amazon.com: Orion Cobalt 2 Channel Amplifier – Class A/B Dual Channel Amplifier 2250W RMS 4500W Max, Car Electronics Audio Subwoofer 2 Ohm Stable Bass Boost MOSFET Full Range Amplifier for Car Speakers
Subwoofer wiring diagrams
How to hook up 4 speakers to a 2-channel amp - Quora