I wanted to keep the factory head unit (LIKE IT) but felt like replacing all my stock 2008 cx9 speakers (non-Bose) would greatly increase my listining pleasure. two weeks ago i started by replacing the front dash speakers with Polk audio 3.5in (DXI350). Feed coming straight from factory unit. The factory front dash speakers where actually just 1 inch tweeters mounted into a 3.5 inch plastic spacer! Cheap! The front door units i replaced with PA 5 x 7 (DXI570) and are also fed by the factory head unit. In the rear of the car i got a little fancier...in the rear doors i installed 8in infinity referance (860W) woofers! i had to modify the interior of the door(a little cutting here and there...) I did manage to get them to fit in the factory position, but required some effort on my part. Once the door panel was put back on...Walla! Factory look! I also added D panel speakers PA 3.5in (DXI350). My CX9 had no speakers back there. (i think only the Bose cars have these...) I am feeding these four rear speakers ( two D panel speakers and two 8in woofers) with a four channel PA amp (PA200.4) mounted under the little storage compartmant in the rear hatch area. The amp gets installed this weekend...so ill let you know my final results...so far its been great! maybe if i get crafty ill even attach some pictures...