O.K. McIntosh, they aren't.
They are 4" speakers at the rear door handle/armrest. The opening will not fit anything larger. Perhaps mods to the door panel might work.
For a McIntosh system, I would think that any number of high-end sound stores would be able to give you a tastful, installation solution. Stay tuned for comments from other members who might be your audiophile peers.
Anthracite/Grey MB Tex
205/55/16, 16x7.5 Lorinser 15-hole
'95 S-500 corners
50% tint all windows