Look online you can find wicked good deals on stuff, speakers in the car are optional but you can replace all 4 for less then 100 dollars and it will make a big difference also its an easy install. A new head unit is also a nice touch but not necessary. As for bass you can get a sony xplod package for 250 dollars which would be fine for your first system then just get a wiring kit which should be no more than 30 dollars.