its not that hard to pull off all the rear panels to get to the speaker holes, bit annoying tho. you can fit some 5" speaker there, just before you buy some I recomend you to drive to the store without the panels and try fit some.
if not just cut it to fit some 6", dnt think you'll have problems with that

I dnt know about the new models, but in mine the cabes for the rear speakers where already pre-setup from factory, left on the passenger side rear panel around the wheel arch, like half way