from that site:
Calculating Amplifier Current Demands
By using the total fuse values of the amplifier, you can get an idea of the amount of current draw that will be demanded under full output power. Although the full output rating is good to determine the total amperage draw in the system, it does not represent the true continuous or averaged amperage draw in the system. Listed below is a simple way to determine the approximate continuous current draw of your amplifier.
1. Determine total fuse value of the amplifier. (Many Amplifiers have multiple fuses built in, simply add the values of all fuses.)
2. Divide the RMS power rating by the Peak power rating.
Example: 50 Watts RMS Divided by 100 Watts Peak Power = .50 (50%)
Once you figure the percentage of RMS vs. Peak power, you multiply the fuse value of the amplifiers by the RMS percentage.
For Example: If the amplifiers fuse value were 30A, then 30A multiplied by 50% would be 15A of continuous current draw.
well, that really doesn't help now, does it!