just asked a buddy of mine on facebook whos an audio installer and heres what he said
you can't remove the speakers from inside the trunk; they're top-mounted on the rear deck. You gotta to remove the entire back seat start with the lower cushion,.then you'll see the bolts underneath that hold down the seat belts and rear seat back. Remove the bolts and pull up on the rear seat back to unhook the top section and remove it. Afterwards you'll need to pull off the side panel on one side; then you can pull the rear deck cover forward and remove it. The rear speakers are mounted on plastic holders that are just clipped into the rear deck....
2000 Suburban 3" lift and some power mods..The daily
06 impala SS CAI,Exhaust,pirellies the other daily
86 camaro Far from stock......The hot rod
1992 camaro RS 25th anv 350 5 spd..The cruiser