STR-K870P is the tuner and the amplifier section in HT-DDW870. AUDIO POWER SPECIFICATIONS POWER OUTPUT AND TOTAL HARMONIC DISTORTION: (Models of area code US only) With 6 ohm loads, both channels driven, from 120 – 20,000 Hz; rated 60 watts per channel minimum RMS power, with no more than 0.7% total harmonic distortion from 250 milliwatts to rated output. Amplifier section Power Output1) Models of area code US, CND (6 ohms 1 kHz, THD 0.7%) FRONT2): 60 W/ch CENTER2): 60 W SURR2): 60 W/ch SURR BACK2): 60 W (6 ohms 1 kHz, THD 10%) FRONT2): 100 W/ch CENTER2): 100 W SURR2): 100 W/ch SURR BACK2): 100 W Models of area code AEP, UK, SP, E51, MX (6 ohms 1 kHz, THD 0.7%) FRONT2): 60 W/ch CENTER2): 60 W SURR2): 60 W/ch SURR BACK2): 60 W (6 ohms 1 kHz, THD 10%) FRONT2): 100 W/ch CENTER2): 100 W SURR2): 100 W/ch SURR BACK2): 100 W Models of area code AUS (6 ohms 120 Hz – 20 kHz, THD 0.09%) FRONT2): 50 W/ch CENTER2): 50 W SURR2): 50 W/ch SURR BACK2): 50 W (6 ohms 1 kHz, THD 0.7%) FRONT2): 60 W/ch CENTER2): 60 W SURR2): 60 W/ch SURR BACK2): 60 W (6 ohms 1 kHz, THD 10%) FRONT2): 100 W/ch CENTER2): 100 W SURR2): 100 W/ch SURR BACK2): 100 W