Quote Originally Posted by Kevio
The amount of average power you need does depend on how far you are from the speakers, how loud you want it to be, the efficiency and power-handling capability of the speakers. Believe it or not, 1 W average is actually reasonably rowdy.
...the type of music you listen to. Yes, most pop music is a little anemic on dynamic swings, but a well recorded classical symphonic piece will put much higher requirements on your gear.

You source will also dictate what you should get - if it truncates the music or has high distortion, then it doesn't really matter what you've got down the line from there. Garbage in > garbage out.