4 Gauge might be sufficient, and if money is an issue, 4 gauge is a heck of a lot cheaper than 0 gauge.
I would run that kind of power on 0 gauge myself though. Remember, with DC power, you lose voltage quickly over distances of wire, and while 4 gauge might be adequate over a one foot length of wire, it might not be OK over the 16 to 20 feet of wire you run the length of your car.
I ran 0 gauge from the battery to the trunk of my car. I chose to run it under the body, and drill a hole up into the bottom of the car (always remember to put a fuse or circuit breaker near the battery). Zip tied it up out of the way of any bumps the car might go over, and used a grommet where it went through the sheet metal, so it wouldn't rub there. The 0 gauge went in to a distribution block, which had one 0 gauge input, and four 4 gauge outputs. That gave me enough outputs to wire my different amps and capacitor with 4 and 8 gauge wire, as needed. Then ran similar disto block for the ground, with 0 gauge to the car's frame at the trunk and at the battery.
Don't pay much attention to brand names with wires. Copper is copper, regardless who made it. Thinner strands inside is better, but the name on the package doesn't matter.
Good luck finding 0 gauge connectors and accessories though. I've never found any local shops that stock them, and even online sites have slim selections. Shop around, you'll find something
*edit* To Will.... bundling thinner strands of wire transfers power better than fewer, thicker strands. That's the way electrons move, they move primarily over the surface of a wire... lots of thin strands means more surface area.
