I have a similar situation with my lusso. Got it as demonstrator fully loaded apart from the DSP.
I hate those empty speaker housings on the rear parcel shelf.
I think the wiring for the sub woofers that go on the parcel shelf is taped up under it.The major problem is the DSP amp itself. It costs around £600. If it's a case of simply changing the existing amp for the DSP one, it may not be such a huge job as the amp is located in the boot near to the cd-rom reader. The cd multi changer goes here as well. The subs themselves aren't that expensive. If anyone has ever done this I'd love to hear from them.
By the way, my lusso is a sportronic, and once you get used to it it's fine. Auto for around town, manual when you want some fun. wink wink