Late Model Mustang power wire routing

Hey guys,

I am going to be helping a friend install a amp and sub in his mustang, it  is a late model, like a 2000 or something.  before I go to help him I wanted to see if anyone knew the best place to route the power wire through the firewall (we're just using 8 guage) I havent had a chance to look at his firewall yet myself and was hoping someone could tell me the best place so i dont waste time

also, he has the mach 460 or whatever sound system, and until he gets more funds to upgrade, he is going to be leaving all the factory stereo in place, just adding the sub and amp. which side should the power cable be routed? Im not sure what side the signal for the factory amps are goin down or if it would really matter in the first place because it doesnt use conventional rca cables to provide the signal

thanks in advance

JAKE

thanks guys,

There should be a grommet but i wanted to ask first.

and yes birdman, we're goin to use a variable loc, we're planning to connect the loc after the factory amp before the rear speakers, this sound right?

also, im planning to use a hot wire from the ignition, hopefully i can pull it off the fusebox like in my integra

Thanks again