Amplifiers are not about power. Power is consumed by the load, whether it's a resistor, a motor or a speaker driver. The amplifier is an energy source and does not necessarily follow Ohm's Law. As an example, if you short a 9-volt battery with a 1/2-ohm resistor, Ohm's Law dutifully informs us that the "power" delivered is 162 watts (9Vx9V/0.5) and the current is 18 amps. Of course that is ridiculous; the energy storage of a 9V battery is limited to about 500 milliamps and only when a resistor limits the battery to less than 500mA does Ohm's Law apply. On the other hand, that 150kVA utility transformer feeding your street can easily slam thousands of amps over a bolted fault. It's all about energy.
An amplifier has an energy source: the power supply's transformer and filter capacitors. If the power supply can maintain it's secondary voltage from any load the speaker presents it, you can call it a "high current amplifier" and relationships established by Ohm's Law apply. But if the output voltage sags when the speaker load drops, then the current delivered to the speaker will decrease, which means the power consumption decreases.
If an amplifier's specs says it can maintain voltage down to 4 and/or 2 ohms, you will see the power double (i.e. 100W into 8 ohms, 200W into 4 ohms and 400W into 2 ohms) and that is practically a true voltage source. But if you see 100W into 8 ohms and 150W into 4 ohms, then that amplifier is not as good of an energy source.