Hello. I recently purchased an Android head unit to replace the factory radio in my 07 Civic EX with premium sound. Only after installing i didn't know I was going to need so much more. I've already purchased a bypass harness (didn't need but may keep anyway), a Scosche unit to use my new stereo with my existing amp, and more. I've been told i may need a line conditioner, which I'm also waiting for, but may lose my sub. I'm new to car audio as well.

So I've been searching forums and checking videos trying to find an appropriate place to run a thick gauge line through my firewall. I see there's a large rubber grommet with other wires coming out of it, but I'm hesitant to drill a hole in my firewall anyway. Some have pointed out a rubber grommet behind the fibers near the gas pedal, but I haven't been able to lift up the fiber pad high enough to see any kind of hole I can route the cable through. I'm sure i even need an amp at this point but would like to know the best place to route the cable through the firewall if I do install an amp. Even though the Civic is ultra-low emissions, I'm concerned about heat, noise, and exhaust coming through the cab if I don't make a tight enough seal. So is there a preferred existing location or is it best to get a hole saw, make a new one, and mount a firewall grommet bushing?