That looks great prop!
Please tell us again, what size those woofers are.
I have retrofitted a factory DSP sub and aftermarket separate amp into my E53 and love the improvement. Now with the separate subwoofer volume control of the Eonon GA6166 it is even better.
I like the factory DSP solution for its enclosure simplicity, its already designed to go into the rear side well of the vehicle.
Getting a nicer sound out of it as opposed to the over 10 year old speakers that are in it would be a another great upgrade even for those of us without factory DSP, IMHO, this is a great, quick and simple sub solution and the enclosures are plentiful on eBay.
Mike