i'm looking for the the easiest spot to route the power cable for a sub amp through the firewall of my 2006 Sonata. any ideas?

Which side of the car is the battery on? What side and where are you mounting the amp? The easiest place to go through the firewall is at the steering column. If you look under the hood you will also be able to see plugs in the firewall where there is a hole but nothing routed through it. You can drill a small hole in the plug and run your cable through there and put some silicone sealant on the cable to reseal that spot in the firewall. Short of drilling your own hole those are the 2 easiest ways through the firewall.

Hope this helps.

There was the same basic thread in the Sonata forum. Depending on the engine/tranny depends on where you can run. My 4cyl 5 Speed has NO unused grommets or easy places to run it through the firewall. My old Corolla was the same way. There is a HUGE grommet with a lot of space behind the drivers side wheel well which is where alll the factory wiring is run from the fusebox on engine to fusebox in interior. You can actually zip tie right next to it from Battery to interior all by pulling the couple screws that hold the plastic wheel liner up.