So I've recently become a new addition to the Patrol family, and loving it, but being only 24 years old, music is still a big thing for me in the car. I know this isn't the absolute most suitable place to be asking for car audio advice since it applies to any car really, and not just a patrol, but thought some of you may be able to help.

I'm just wondering, as in the past, I've only had upgraded head units and at one point an amp and subwoofer, but being a nice big beast of a patrol, what would be recommended in terms of upgrading?

I'm looking at a new head unit, maybe some new speakers (How many do I need? Are there only 4?), and also a possibility for the future being a new Amp and Subwoofer, where would you recommend I put these in the patrol?

I'm planning on buying the parts online and getting them installed separately somewhere else (hoping to find it cheaper that way than paying somebody like JB Hifi or Autobarn). Can anybody recommend places that can do a good job of installing car audio in the Northern Suburbs of Melbourne? What about sound deadening for the doors, etc?