I just finished replacing the door speakers. The two front doors, Infinity 6020cs (component system, 6 1/2" mains, 1" Tweeters, Crossover boxes) installed mains and tweeters behind door panels (no cutting just drilled holes to mount) left the factory Tweeters in the window pillar (airbag in the way). The two rear doors, Infinity 6022i (standard 2-way). The factory head unit is a standard single disc player, The sound quality that I'm getting out these speakers is phenomenol. The factory unit has no problem driving these speakers. My Wife can not believe the difference it has made, the highs, mids and lows are crystal clear. The factory speakers that were on our Acadia were the cheapest speakers I think GM could buy (old paper type) if they paid $5.00 a piece that was to much.
Our Acadia is now 8 months old, I should have done this 8 months ago. Total cost of project $342.00, 4 hours of not so hard work.