anyone know how deep is the space where the rear speakers are?

could i fit something 3.75" deep or 4.75" deep?

>

You can fit up to about 7" deep so yeah, no problem.

oh ic.. hm.. what's the biggest size speaker i can fit in there diameter size?

can i fit speakers with
6" mounting diamater and 7" overall diamater
or
7.125" mounting diamater with 8.375" overall diameter?

>

Probably but you might have to make your own mounting bracket.

Also, remember that the speaker opening in the trim was designed for the factory speakers, so you'll have to do some customization for anything larger than that.

If you want some pics of the rear speaker with all the trim removed, email me. I don't know how to upload pics to a site to add them here and it's probably just easier to email them.