Gm-a6704 gm Series Class Ab Amp (4 Channels, 1,000 Watts Max)-Black. From dramatic distinction to dramatic design, GM Series car amplifiers are thrillers in every sense, pushing the limits of flexibility and functionality. The 4 channel GM-A6704 car amp delivers plenty of juice to your speakers. It also automatically selects the proper input signal mode--either RCA or speaker level plus it will turn on automatically when the receiver is turned on.