more important than the wattage is the impedance (ohms), ideally this should match both output of the receiver and the input of the speakers or you could overstress the receiver or the speakers depending on which is higher/lower. Not matching impedance has different problems, like excessive power usage, noise, interference and distortion.
The wattage of the speakers is usually the max sustained power before they blow up or become damaged. Any wattage less than that will drive them, but based on the impedance difference, it may require more power to deliver the same amount of amplification.
tl;dr: match the ohms.