I am about to pull the trigger on a order. I go to the Infinity home site to see what the 05 reference series offers, I punch in my car and once again the sizes do not match what I have been told here. I of course will take the advice here of 6x8 front, 6x9 rear deck but the site says 6x8 all around and when I try to order the 6x9s for the rear on a couple of sites it comes back with does not fit your vehicle. Damn!!!!

 

For instance at crutchfield, says these do not fit rear deck

http://www.crutchfield.com/S-NgjUpeo...300&I=1089613I

 

If you do some search on the forum, you will see that everyone installed 6x9 in the rear and that it was a drop-in. I did the same so I know for a fact that the rear was a 6x9. Unless the replacement 6x9 speakers are oversize (is there such a thing?), they will fit fine.
The other possibility is that for those Infinity Reference speakers, the tweeters protrude so much that they won't fit under the stock grille. This might be the reason why some sites say similar things about other 6x9 speakers.

Otherwise, 6x8 front, 6x9 rear. End of story.

 

Makes sense. I wasn't questioning you. I am just having trouble ordering them because the site says no go.