Started with this.
Bought some new speakers and sound deadning stuff and applied to door panel and door.
The reduction in road noise and general rattles is astonishing. For instance I can hear the exhaust tone much clearer now and at speed, if you have music on, it doesnt sound like the band are playing from the back seat

The whole care somehow feels more solid. And for those of you thinking the solidness has come from loads of added weight; the total weight for the two doors is a little over 2kg so I've added about 1kg of weight evenly per side towards the centre of the car. I certainly havent noticed any difference in handling etc and I seriously doubt there actually is any (ducks to avoid a flaming

) I've been careful not to cover any screws / nuts / central locking gubbins etc as I dont want to have to pull it all off as soon as something develops a fault! Anyway, I'm well pleased with the results of this mod, I was expecting at best a minor improvement but the difference is really noticable.
Regards
Shaun