I have a 2000 Z3, and am replacing the original Blaupunkt head end, this model has 2 front spk's, 2 back, 2 door, and a blown sub in the back between the seats. Ordered a repalcement sub that will fit in the housing under the 'T'. Trouble is I am not sure how the Sub is driven, there is no amp, have looked hi and low. What does the group thnk is driving the Sub? The head end?