[soundman98]

major difference between the front dash speakers and rear speakers is that the dash speakers have a capacitor that drops bass response below (IIRC) 6khz. an oem version of the name-brand product "bass blockers".

there's nothing wrong with installing 6.5's back there, but with just the L-bracket hanging back there, there's neither the vibration resistance support, or even a a concept of enough of an enclosure to get any sort of reasonable response out of them.

so the solution to a larger speaker is both a new bracket that better supports the speaker from 3 points instead of just 2, as well as building some sort of back-box/enclosure to better the bass response.

but all of that only works if you've already replaced the head unit, as i'm led to believe by others that have tried it that the oem head unit doesn't provide enough wattage or a full frequency range to the rear speakers.

mine are still installed. but disabled at the head unit. i don't miss them.