How can a speaker have a higher output power than input
The 92W is an "average" figure while the 1kW is a "maximum". To get a true idea of the maximum input power it could draw, we'd need to look at the information plate on the mains input. There will be capacitors in the power supply for delivering power into peaks. If you actually got it set up and outputting at peak volume it would probably draw >1kW from the mains.

It's not unusual for speaker power outputs to be really misleading, although this is the Panasonic official website and they quote RMS and PMPO. 1kW is quite loud!