There are no wires in the rear doors if the car was not specified as having rear speakers. likewise there are no wires are amp in the drivers foot well hidden compartment
I spent yesterday afternoon retro fitting rear speakers to my silver TDI and did the same retro fit about 15 months ago on my other TDI
You need the speaker and tweeter from the front or rear doors from a breaker (the speakers are all the same front and back left and right as are the tweeters)
You also want as much of the loom as you can get from the breaker, if you get enough of the loom it will include the connectors to the speaker / tweeter and the wire between the two. You then solder some medium duty speaker cable to the end of this loom and feed this through the gaiter to the B post connector.
Now you have a choice, you can either (a) fit the correct connector terminals in both the socket and plug and continue running the wires from the B post connector to the head unit or into the drivers foot well to the rear speaker amp or (b) utilise the small space under the B post connector and feed the wire through this space (I chose this method) then add a piece of heat shrink tube to protect the cable in this area, I also left about a foot of cable coiled up in the B post inside the car, just in case I need the doors off in the future, in which case there is enough cable to allow a suitable connector to be fitted (bullet type would seem appropriate) I chose not to fit the connector as it introduces an unnecessary failure point.
Once you have the cable inside the B post the trim panel easily pulls off and you can route the cable down the front of the B post and along the sill utilising the original cable loom clips, then in my case across to the head unit as I am going after market head unit. If you want to keep the stock Audi head unit then you need to route the cable into the drivers foot well hidden compartment, buy the rear amp and install it in here with the necessary power and audio feeds from the head unit to the Amp.
The speakers bolt into the doors using (I think) 5mm bolts 4off per speaker, the aluminium door panels have the inserts in already their hidden under the foam cover which you need to remove before fitting the speakers
Hope this helps
Cheers,
