Tell us about yourself!
You say it`s powerfull but don`t mention what power it is or even how to calculate its power in watts.Also it`s all very well saying in the ciircuit diagram "to phone jack" but you don`t show how the wires are conected in the stereo jack as you only have one chanel of the stereo phone socket connected to the speaker.
This is the type of instructible I avoid. Its like saying 1 bye a ford engine, 2 buy a ford body work, 3 buy ford wheels. Put them together and you have a Ford car. It`s crapsmanship and must be avoided.