I installed the Blaupunkt IC 109s which were mentioned in another post and they were a direct replacement - used existing grills, mounting hardware and wiring. They weren't expensive and good replacement for the OEM VW/Blaupunkts which were in there for 29 years prior.. I'm sure there are better quality speakers out there, but these were pretty nice for a stock setup.
Mk2 Scirocco Storm
Mk3 Golf GTI VR6