You're confusing audio line wattage and power line wattage. And audio wattage is marketing crap. Reality is most audio anyone hears (outside of a concert setting) is below 1w of power.http://www.fat-man.co.uk/docs/product_07/Carbon_Trinity_Hybrid_Valve_Amp_with_Speakers.shtml
Their flagship dock. It's a beauty.
And yes, this can actually blow up your iPhone. It pumps 50 watts of electricity, which means there's 10 amps of power to be dealt with at 5V.
5V 10A and 50 watts? Here's for a comparison. Turns out, that cube charger that comes with your iPhone is a monster. It pushes out 1A of power. How's that for a comparison?