S60R Audio

I got everything I believe on my S60R except navagation. I am looking to put nav in and to go with the stock system setup. It would cost somewhere near five thousand dollars to get the new dashboard setup. So I was looking at the available systems out there, and was wondering if I was going to lose the surround system that comes with vehicle or if there is a system that I can replace it with that would take advantage of the current speaker system,

Thanks.