Volvo sells a handsfree setup for S80s but from the one Erikson unit I saw installed, it was not a good phone setup and the customer had nothing but problems with it. The '03 S80s have an optional phone system that's probably very good in comparison but I doubt that those can be retro'd into older S80s. I'd opt for an aftermarket hands free phone system for your '00 S80.
As for XM radio, Volvo doesn't have any provisions for any satelite radio system so far but you can easily add the universal XM or Sirus radio systems to your car (or ANY car) by tapping into the radios antenna lead which is how that's done. The kit includes a receiver and you'll need an XM antenna but it installs easily to any car. Before my old cd player died, I used the universal XM radio setup and it works fine. My new cd player was XM ready.