The Orion CS 100.2 amp is rated for 100 watts RMS per channel at 2 ohms.
To obtain amps from watts a voltage must be given.
The Kenwood KAC-744 amp has a power handling capacity of 50 watts RMS per channel at 4 ohms.
50 Per Channel
A 20 amp breaker can handle up to 2400 watts per hour (20 amps x 120 volts = 2400 watts).
The Kicker Impulse 352xi amp has a maximum power output of 35 watts per channel x 2 channels at 4 ohms or 35 watts x 2 channels at 2 ohms.
The Audiobahn amp A2601Q model has a maximum power output of 2600 watts.
The Alpine V12 MRV-T501 amp has a maximum power output of 500 watts.
120Watts=1Amp
A T1000 amp typically has a power output of around 1000 watts RMS.
The wattage of a factory amp can vary depending on the make and model of the car. On average, factory amps typically range from 10 watts to 50 watts per channel. It's important to check your specific car's specifications for the exact wattage of the factory amp.
Power = volts x amps, so your example will be 12 x 0.5 = 6 watts. (500mA = 0.5 amp) Note we don't talk of 'watts per hour', it is just watts. 1 watt = 1 joule per second