What are you looking to power? No computer should need even 1 4 AWG wire, if you are installing a few thousand watts worth of amps as well then maybe you need that kind of capacity.
I have a probleme I can not pass a 0AWG from the hood to my truck is 3 wire 4 AWG will have the same capacity of the 0AWG.
You can use 3x 4awg, they should work just fine.
I almost had to do that too.
Use a grommet and fuse it at the battery connection. If you short a wire that big without a fuse, you'll get a fire in the insulation and maybe in the car.
I will have a 600watts inverter and for now 1 amp of 900 watts soon another of 1600watts amp. a second battery in the trunk and to a complet that a 2.4 farad capacitor.
Name the amps being used. Amps are all rated so differently and people dont know what #s to look @. if your amps will be pushing that much power from the RMS rating there is no doubt you need to run 0ga.
also what subs and impedance?