Although this idea has become increasingly popular, we don't recommend applying more power to your speaker system than it is designed to accept. Exceeding the power handling capacity of your speaker enclosure is considered misuse and can render your warranty null and void in the event of any damage to your loudspeakers.
Underpowering your speaker system by too great a margin can be dangerous, too. Constant clipping of the power section of even a 100-watt amplifier (to get greater apparent volume than the amplifier can effectively produce) can damage speakers rated to handle much greater wattage. "Clipping" is the distorted signal generated by an amplifier that is being operated over its capabilities, and describes the actual "cutting off" of signal peaks at the amplifier's power limit. This is the sound often heard when a system is played too loud and the sound starts to "break up." Clipping distortion is the most common source of speaker damage, due to the near-DC content present in a clipped waveform. Those unaware of this may assume that they can turn their volume control up to maximum because their speaker system is rated to handle significantly greater wattage than their amplifier is rated to deliver. As explained above, this is simply not the case and should be avoided.
The best overall solution is to assemble a system of components that are equally or closely matched in terms of power rating/handling. For example, an amplifier with a power output of 500 watts RMS at 4 ohms connected to two 8 ohm speaker enclosures, with a power-handling capacity of 250 watts RMS each, would be considered a well-matched and recommended system.