So I recently purchased a 2002 Volkswagen Jetta off of a friend of a friend. Today, I played some music and the sound quality was horrible!! :/  It sounds muffled and shaky.. I tried to adjust the treble & bass but that didn't make a difference.  I want to have a new system put in, do you think it'll fix that problem?  If so, what exactly do I have to get? I don't know anything about sound systems or cars lol..  What brand do you reccomend??  Thanks!!