The car still had the original OEM speakers fitted - they are sort of ok at low levels but that's about it. I decided to swap them for a set of Hertz Coax speakers since i want to keep the interiour looking "unmodified" for the moment - and the Hertz are supposed to have a good efficiency.
OEM speakers still looking good / undamaged - not bad considering 15 years of age!
In with the new - straight swap only hat to drill an additional hole into the speaker frame. I added a foam gasket beneath to seal the speaker to the door. Other than that, the doors will stay untouched from sound deadening - don't really see the point of this in a light weight softtop Roadster and i've got other cars to play with I.C.E ;-)
However, while i was at it, i took the opportunity to spray the window rails with grease and the doors with corrosion proofing.
Finally i got out the Meguiar's PlastX and attacked the rear window - got out a fair bit of the scratches and the plastic is more clear now. There still are a lot of deeper scratches left, so I'll have to repeat the treatment a few times. No pictures though, but that's the stuff - overall i can recommend it!
Oh,before i forget, the sound quality has of course improved dramatically, now one can at least enjoy music at reasonable levels - there even is some low frequency dynamic now :D