HD900/55 channel amplifer 100 watts RMS x 4 at 4 ohms + 500 watts RMS x 1 (at 1. 5 4 ohms) 75 watts RMS x 4 (at 1. 5 3 ohms) + 500 watts RMS x 1 (at 1. 5 4 ohms) 150 watts RMS x 2 bridged (at 3 6 ohms) + 500 watts RMS x 1 at (1. 5 4 ohms) variable high pass filter on front and rear channels (50 500 Hz, 12 or 24dB octave) variable low pass filter on subwoofer channel (50 500 Hz, 12 or 24dB octave) subsonic filter on sub channel (24 dB oct at 30 Hz) removable