Routing options for 1/0 Gauge Power Cable

I need to run 1/0 gauge from my engine compartment to behind my rear seats (DCLB) to power my amps (1200 + 600 watt amps split down to 4 gauge). I have several options, but maybe someone has already worked it out. I can run it externally, along the frame, and up thru the bottom floor behind the seats right where I want it. The wire is protected by fuse at battery in case it shorted down the road. I can also run it thru the firewall and along either side. Not much room though due to the size of the wire. Or I can run thru firewall and along the center console route to the back. The exterior route seems easier, but not sure if having the wire running outside weather conditions is worth the tradeoff and if exhaust heat would be a concern. There's definitely not enough room in the factory wire harness trays along the side to fit the large wire. So that leaves running on the sides under the carpet, or along the center console under the carpet. If I go thru the firewall, I'll probably need a universal firewall boot like the daystar to seal it all up. Same if I go up thru the bottom. Thoughts??

 

Firewall. Only way to go IMO.

Don't have pics as my truck is awaiting a frame but that's what I did with my 2010.

 

I have 0/1 guage going through the firewall just underneath the master cylinder and brake booster unit with a gromet, no problem and ran the wire down the drive side where the factory wiring goes no problem the only spot where you might run into some resistance by the rear door where the two trim pieces meet, it gets a little tight in that area but it will fit with some persuasion.

 

Does anyone have any ideas on running 1/0 power and ground along with new speaker wires and a run of speed wire from behind the back seats of a 4 door 2021 Tacoma?