I'm about to buy a Pioneer Elite VSX-82TXS and a few other components that I plan to run off a UPS. The Pioneer is 130w per channel and does 7.1 so in theory could draw 910w. What should I expect to actually draw? I'm only using it for 5.1 so can I disable the two other channels or do they use no power if nothing is plugged in? Also I'm in an apartment so I'm only listening at low to medium volumes.