Car Speakers

I recently installed two brand new pioneer speakers and a brand new alpine radio to my audi a4 2001 quattro. the sound is great at low volumes however when the volume is turned up moderately, a slight static can be heard from the speakers, correlating with the song playing. it is not a constant static, only during certain parts of a song. voices from am stations also often cause static. the thing that is weird is that the static happens only on certain songs. one song may come on and i can play it loud no problem and then another one will come on and my speakers will go crazy with static. the static sounds like white noise but very loud. , any ideas?

Stereo too strong for speakers. it is called distortion.