Brakes (discs and pads) what should I go for ??

I'm looking for some advise from those that know more than me (which is quite easy as I know naff all)

I need to change my discs and pads but would prefer something with a bit more stopping power than the originals, I'm not looking for a G60 upgrade, change of calipers or bigger servos, I would just like to change the discs and pads.
On hunting around Black Diamond seem to be a reasonable compromise, cheaper than Brembo but with better performance than the originals.
Does anyone use these, or are there any alternatives I should be looking at ?
Also, there appear to be a couple of different sizes available : 10, 12 or 20mm - I've an 89 GTI cab.

All help and any ideas most appreciated.

Cheers

20mm vented 239mm discs are what you have, same as mk1 and mk2 gti 8v