why on amazon may i ask

Amazon.com: Used and New: Cadence Acoustics ZRS C9 600 Watt Peak 16V 4-Channel Class AB Amplifier

also a lil better amp, same place aq is made in korea. amazing amp

Amazon.com: MB Quart ONX4.80 4 Channel Amplifier 4 x 80 @ 4 OHMS, 4 x 160 @ 2 OHMS, 2 x 320 @ 4 OHMS: Car Electronics

good amp not qute up 2 the cadence or aq though

Amazon.com: Q4.80 - MB Quart 480W RMS 4-Channel Q-Series Amplifier: Car Electronics
a lil better mb quart