In my 2003 LS6, I have the Alpine in-dash 6 CD player but (2) speakers in the front console, (1) in each door and (2) mounted under the rear deck not in a box - i think that's only 8. am I missing a few ?
i think you'll find the Infinity speakers sound "bright"; Polk have more mid-range. Whatever you get, match them from the same company to get the best sound.