I think you'll find you have no analog connections for an amp on your blaupunkt unit.
This will involve a high pass filter connection at your amp.
You would need to run all your speaker wires to the amp....messy.
If you wanna save the wiring trouble, best fit a MP3 player and start off using the factory wiring/speakers. Up grade later, slowly.
There are a couple of options available for filling in the gap below the audio unit and I believe a wiring patch harness is an option to make wiring up easier.
I found all this at Autobarn.
Have fun!
