Hello! In my Golf IV (two-door) I only have the factory (2oW) speakers in the front doors. Now I would like to replace them with better ones (50W), plus two more rear ones (currently only glare available). Since I have little idea in this area I would like to let experts do it myself. So that I have a clue: What is a fair (normal) price for such work?: replace front speakers, rear ones which, cabling Thanks in advance, mf g aedificans