How to wire a powerful amp with two speakers to avoid damage

Sean is correct. More speakers get damaged from underpowered amps than from overpowered ones. The amount of power delivered to the speakers is dependant upon the voltage delivered to the speaker, which is dependant upon the volume control. If you play the speakers at a comfortable level the big amp will not harm them in any way.

The heat generated by an amp is mostly caused by the current in the output stage. In a pure 'Class A' design the output current is at a very high level all the time and thus the amp is hot all the time. In a 'Class AB' design the output current is at a low level unless a lot of current is being delivered to the load. Under low listening levels or with very efficient speakers the output current is small and the heat being generated is also small.
Chris

Thank you, 1439bhr, for the excellent explnation as to the damage caused by under powered amps. I like to see posts that explain why things happen so that everyone can better understand what is happening inside their 'black' boxes. I hope to see many more posts from you. Chris

Most amplifiers supply voltage to the load (speakers) and the impedance of the speakers at the frequency being reproduced determines the amount of current flowing. A battery is also a supplier of voltage to a load. The bulb of a flashlight uses less current than a headlight of a car. An amplifier is like a battery and is happy to deliver whatever current is needed up to the point of its max output current.

The only other factor that effects both the battery and an amplifier is heat. Automotive batteries can supply much more current at 25 deg C than at 0. An audio amplifier usually sounds better after it is warmed up and is probably the main concern in an over powered "class AB" amp. A high bias amplifier should not have any problems driving even a pair of headphones because the high bias will keep the amp warm even with no signal applied.

The analogy of an amplifier and a car is not correct because an audio amplifiers voltage and current are a linear relationship while the RPM and torque curve of an engine is not.