..5 1/4's speakers fit with minor modification in the rear side panels. The OEM speakers are 5", so there was some modification to make them fit. drilled 4 holes at the 5 1/4 mounting points, very easy install. Sound benefit was outstanding.

If you are planing on, or allready have a subwoofer, you really don't need bigger speakers in the rear side panel's. I cut out the bass to all four and let the sub handle that range. There is no clipping, the sound is very loud and clear. Using 600hz bass blockers on the 5 1/4's and 300hz on the front 6 1/2's.

Good luck with your choices, everybody's taste in audio varies, so by all means do your thing