My son has purchased a powered sub woofer for his 2005 Crossfire SRT6 coup. I have installed one of these before in a 2005 Jeep Grand Cherokee Limited. The hardest part of the job is running a thick power wire from the unit to the battery. I need to pass through the firewall somewhere. I really, really do not want to drill a new hole. Where is the easiest place to access a rubber grommet and get this job done?