WHAT AMPLIFIER, WHAT SUBWOOFER?
Note: In order to obtain the best amplifier / subwoofer performance without failure even when according to the below charts.
1/ DO NOT raise the headunit's volume to its fullest.
2/ DO NOT set the amplifier's input sensitivity to its maximum, and always set to match the combining headunit's pre-out level
If you do not follow these two rules, clipping signals will output from the amplifier, which will result in speaker damage.