No, stock size is 6x8 fronts and rears. 5-1/4" (and apparently 6-1/2", I don't know how) speakers are compatible as long as you have an adapter which Crutchfield will supply (others too, at a cost). Pioneer Premier's D and PRS series 5-1/4"s are supplied with 6"x8" adapters.
I just got Pioneer Premier TS-D820Ps 2-way coaxials for my rears, I got these speakers not much for the power - you don't want the rear speakers to be that powerful anyway - but because they are one of the few coaxials out there with a true crossover on board. They sound fantastic. I didn't go too all out with the rears, from a drivers and passengers perspective you hardly hear the rear speakers anyway, they just provide sound space from the rear. With baby coming along anyway I'd likely turn them down, but I wanted something that sounded decent enough for the drive-in theatre when we sit in the back hatch up. I just wanted simple plug and play installation as well.
I'm planning to get either Premier TS-C520PRS (top of the line Pioneers) components or Hertz HSK-130 (second top of the line from Hertz) or Hertz MLK-165 ($799 MSRP, could probably get them for $600, but these speakers are just the best of the best, the bass is strong and clean, the tweeters plays details so fine you just want to turn the treble all the way up) components for the fronts, they're both 5-1/4" round (except for the MLKs, they don't come in 5-1/4") but in general everyone says that round speakers produce a superior sound to oval speakers.
joeym509, you have to show us how the 6-1/2"s fit. I really want the Milles!
