motor wattage
Since the United States uses 120 volts, the motor wattages probably never got as high as they did in Europe, although 240 volts is actually more efficient. With 120 volt motors, they draw more amps. As Tom said, 900 watts should be enough to clean just about anything. I think the model 88 airway uses an Ametek motor that I am quite fond of, I have a compact C6 that has the same motor and it has no problem cleaning anything. I also have an Electrolux 1205 which uses the 575 watt motor, again, no problems with cleaning. The newest Numatic Henry uses a 620 watt motor, it's very quiet but very powerful. As long as there is enough suction and airflow to pick up the dirt, the machine has enough power. And, many of the lower watt motors sound much better than the high power screaming jet motors that are so common in vacuums now. In the United States, the motor used in the Miele canisters is 1200 watts.
Mike