I'm gonna try some things tomorrow that I read from crutchfield... I'm just wondering what are the most likely causes of noise when the engine is off... all the documents merge ground loop noise and alternator noise together.

Is it possible that the noise is coming from my power leads? or is that just for alternator noise?

Tomorrow I'm gonna try regrounding the unit, adjusting amp settings, checking amp power connections, and... I dunno, any more tips?