Looking for a simple solution to the problem of needing to cross through the firewall to bring an 8 gauge power wire to the new subwoofer in my Santa Fe Sport, I found what is likely to be an easy way for most Hyundai models.
Just to the left of the OEM factory wiring for the steering wheel wiring, there is a very quick and easy way to run a single wire along side of the existing wires. Most of the time what you find is people recommending that you poke a new hole through the firewall next to or near an existing opening. Using this spot doesn't require a new hole or any poking / cutting / knife into the firewall, you just take your time and adjust the existing grommet so that you can add another wire (or two). The wire ends up coming out right next to the fuse block under the hood, and you need to go to the battery, anyway.
The end result is a neat and clean single wire next to the battery. Here's the end result for my wiring. Sure, I could have used a black wire (red?) instead of the blue one and been more discrete, but that is what came with the 8 AWG kit.
The 30w fuse is what you see next to the positive side of the battery.