Audi TT Concert Stereo wires

Hi

Can anyone tell me which each wire does, eg which ones are speakers, power, clock etc.. 

I'm fitting an after market stereo and dont know which wire connects to what. There doesn't seem to be clear speaker wires, front left +/-, front right +/- etc. Im wondering if the wires go to an amp in the boot then come back out, as different colours, to the speakers. I took the drivers door card off and the two wires going into that speaker didn't correspond with the wires behind the stereo. If so, will a universal harness adaptor work, as in, if the speaker wires coming out of the new stereo, to the amp in the boot, will the affect the sound? 

Ideally, I would just like someone to list which each wire is on the image I have attached.

Thanks

Dan