Цитата:В YAMAHA RX-V863 почти 1 КВт - там 850 Вт...

...откуда такие данные?
В топовой Yamaha DSP-Z11 (с ее 34 кг. веса) всего 800 Вт.
   
...мануал 167 стр.
GENERAL
• Power Supply
[U.S.A. and Canada models] ................................................ AC 120 V, 60 Hz
[Australia model] ................................................................. AC 240 V, 50 Hz
• Power Consumption ................................................................. 800 W/1000 VA
• Standby Power Consumption ........................................................ 0.1 W or less
• AC Outlets
[U.S.A. and Canada models] ....................... 2 (Total 100 W/0.8 A maximum)
[Australia model] ........................................................... 1 (100 W maximum)
• Dimensions (W x H x D) .................................................. 435 x 210 x 497 mm
• Weight .......................................................................... 34.0 kg (74.0 lbs 15 oz)