Sony Xplod XM-GS4 4-Channel Car Stereo Amplifier (Black) The XM-GS4 4-channel amplifier is engineered to enhance every track-including high-resolution audio files-thanks to an ultra-wide frequency range that extends up to 100kHz. A range of premium circuit components work together for ultimate efficiency and pitch-perfect sound reproduction, so you can give every road trip the soundtrack it deserves.