Drilling the firewall for Subs

ok so I am installing a totally new sound system in my 2003 buick lesabre custom but I'm not sure where the best place is to drill the firewall and i dontg really want to just start poking holes. I was thinking about drilling through on the drivers side near the pedals or going through the glove box. I think that there might be an empty space between the glovebox and the firewall and i really dont want to mess up my air bags or anything else. Any tips at all will be helpful.

I ran a wire or 2 through near the pedals on my '97. The 03 might be quite different though. I went through a rubber boot or grommet down near the brake pedal somewhere. from what I recall, it was a little tricky to pull through on the engine side. Behind the glovebox would be more difficult.