$1500 budget this is so simple. sub stage: sa12
$1380 amp: q1-1200
$ 1100 wiring: knu concepts 4 gauge with some 10 gauge speaker wire, less than 100 ft total wiring. estimated around 50-80
$ 1120 headunit: JVC or pioneer, something to start off with. both have decent entry level models for under $90
$ 1030 enclosure: custom 50-70 that's the 1 sheet of mdf and all the materials needed to make it. nails, glue, liquid nails etc.
$ 960 door speakers less than $100 depends on you and your choice.
$ 860 install your system. $0.00
$860 throw a bbq, buy some beer, and do absolutely nothing all day but listen and admire your system