I am installing my new system into my car and we are going to make a custom box. First I don't know what wiring kit to get. I have 3 JLw3's and a Precision Power 2150 Amp. I am thinking 4 gauge?? Also what tools would I need for making the box, running the wires, putting on the carpet, and so on...

 

4ga is what you want for power and ground. Be sure to fuse your power line 8" from the battery and use wire loom on it under the hood.

3/4" mdf, wood glue, drywall screws, standard sillicon, carpet, spray on contact adhesive, razor blade

 

You forgot some other tools:

Bench saw
Jig saw
Drill with Phillips tip
Measuring tape
Square ruler or "T" ruler
Utility Knife or X-acto knfe

 

Don't forget the beer to calm you down when you make a cut and the damn thing is 1/4 inch to short or when you are screwing the boards together and you chip a corner off.

 

D'oh! definetly can't forget the beer

I figured common sense would tell them what is needed to cut wood and assemble a box