The standard speakers are cheap 16.5cm 2 way components. The main driver is in the door pocket. This is easily removed by locating the slot to pry it off with a screw driver. The slot is at about the 7.30 position.
As far as fitting new 16.5cm speakers in the door goes. One option is to buy the Autoleads Mk4 Golf speaker adapter and cutting off the lip so it fits (part no. SAK-3103) or if you're pulling the door apart a proper wooden baffle may be a more suitable solution.
Unfortunately the tweeters are a bit of a pain. I believe they are glued into the door next to the door handle. To remove these the door card must come off.
I've yet to find a write up on
how to do this, but will do it myself when I get the replacement audio kit.
Similiarly to you MatG I intend to swap out the speakers for a decent set of component speakers and a sub powered by a decent amp.
Could you suggest a suitable line driver to get the speaker level output to low level. I've seen a few options, but not really sure which is the best way to go to ensure the best sound quality.
Cheers,
Dash