If you have 2 speakers on 1 channel ,and it will be a 2 ohm load ,and at 2 ohms your amp will put out 300 watts.Then each speaker will be getting 150 watts .So weather you use 2 channels at 2 ohms or the 4 channels at 4 ohms,you will still get the same amount of power to each speaker. An amp runs cooler and more efficient at 4 ohms than 2 ohms.Also keep this in mind ,if you have a class a/b amp its probably 60% efficient .So at 100 watts you really are only getting 60 ,and thats probably rated at 14.4 volts ,and your car wont stay at that voltage so that will bring down the power of the amp also.Hope this helps .