the most immediate upgrade on your system will be coming from your speakers. if you change the stock with targa which cost probably less than 2k, the sonic character will change and it might even appear cleaner sounding than what you had before. deadening is a very tricky part, and not everyone will appreciate this upgrade immediately. in deadening, it is like building a solid rigid enclosure around your speaker rather than just adding weight on your doors. when done right, midbass response should improve.