I pulled the panels, and found some 6" speakers. I was able to mount 6x9s, without modifying the vehicle, and kept the stock appearance. I had to drill 2 small holes in the plastic speaker mounts, and mounted the speakers horizontally. Speakers are mounted about 2" back, and 2" down, from stock location. Pics below.

 

Nice work!

 

A delco speaker though?? Surely every other brand ever would be better sounding

 

That's the stock speaker. I can't control what Pontiac did my Sophomore year of High School