The ATI AT 6004 amplifier and all AT6000 series amplifiers are rated at 300 watts RMS/channel into 8 ohms from 20 Hz to 20 kHz with no more than 0.03% THD with all channels driven and 450 watts RMS to 4 ohms under the same conditions. The ATI AT 6004 amplifier has a signal-to-noise ratio that is typically referenced to 128 dB at full output, so each amplifier in the series is capable of reproducing the full dynamic range available in today's lossless recordings. The AT6000 is available in 2 to 7 channel configurations and can be upgraded by adding 300 watt power modules. Each model comes standard with 2 massive toroidal transformers with quick connect plugs..PZA MORE SPECS