If it's a 4 cyl, you don't need anything bigger than 4 gauge, but 2 would be preferred. That is plenty overkill for a trunk mount battery. There is no "withstanding the higher current flow", you need large wire so the resistance will be low over the distance that you'll be running the wire. Resistance versus current equals voltage drop, which is the enemy. And don't go for the "bigger is better" mentality, you're just wasting money if you use wire that's larger than you need. Put a fuse or breaker at the battery end of the cable for safety, if you get in a wreck or the cable gets cut, etc., the fuse will keep your car from burning to the ground. Car audio cable works fine but the insulation is usually junk, battery cable or welding cable is usually cheaper and has higher quality (higher temp, better abrasion and solvent resistance) insulation. It may not be as pretty, but who cares.

Do not use solid conductor house wire, it will fatigue.