Yamaha XM4080 Four Channel Amplifier. Stereo: 90 Watts/ch @ 8 Ohms, 120 Watts/ch @ 4 Ohms. Bridged Mono: 2 Channels at 240 Watts @ 8 Ohms/ch. 2RU.

Yamaha XM4180 Four Channel Amplifier: 210 Watts/ch @ 8 Ohms, 250 Watts/ch.@ 4 Ohms. Bridged Mono (2 Channels): 500 Watts @ 8 Ohms/ch, 300 Watts @ 70 Volts/ch. 2RU.