Short heads-up for folks looking for a (relatively) cheap upgrade from the original paper speakers and who want to retain the original grills without cutting.
The Alpine SXE series are a perfect match.
Link SXE-1325S for the front 5-1/4 and for the back
Link SXE-4625S in 6x4. They come without a grill. I haven't installed them yet but it couldn't be any worse than the stock set-up (original Blaupunkt Monterey plus Blaupunkt speakers)