Audio Systems: Wire routing, jeep cherokee sport, jeep cherokee

Question
I have a 99 Jeep Cherokee sport (4-door) with a 4.0 6-cylinder.  I'm in the the process of adding a sub box and amp.  While running the amp power wire from engine compartment to amp, other than drilling a new hole in the firewall, is there an easier/better route to access the interior of the vehicle to run the wire?  

Answer
Sorry, I haven't answered for so long cuz I've been trying to find one of these vehicles to take a look!  closest thing I found was a wrangler. there was a rubber plug on the firewall on the driver's side,  the battery was on the passenger side. so you'd just poke through that rubber plug.  Most vehicles have these, sometimes they're hard to find.  sometimes you can find them by tracing the existing wires from the battery and see where they go through.  usually theres a rubber plug that you can just shove a screwdriver though to make a hole and feed a few feet of wire through that hole, then look inside the car and hopefully you'll see the wire on the floor somewhere.
Good luck!  sorry I don't have an exact solution for you, just a general one.  If I can be of any more help, please let me know.