[flyingfrizzle]

Far as the wattage difference you probably wont notice a difference coming from the head unit built in amp. Now 40 watts from a built amp in the head unit vs an external 40 watt amp, you will notice a BIG difference. The built in unit will do fine for listing on the boat for good sound but if you really want to crank it up like at a sand bar loud you would want to look at more power from some external amplifier power. Also when looking at watts pay attention to RMS power (watts) vs MAX watts. The rms is a continuous power and is best when judging what you really get. Max is an maximum during burst sections of music and those numbers are usually inflated for sales purposes...