Yank the V6: too much trouble to do a custom turbo or blower install.

Drop in a built turbocharged four banger, or a built chevy 350.

It's an inline 6, not a V6.

The S80 T6 used a very similar engine with twin turbos, I believe the
compression was lower and a different engine management system.
Personally I'm a big proponent of turbos, they're much more elegant and
efficient. I think your best bet would be to find the T6 motor and use a
custom fuel system like Megasquirt, or at least use MS on the motor you
have. Adding a turbo requires some special considerations so you don't
blow the motor. Motors that came with a turbo to begin with are a better
bet.

Well, first it is an inline 6 and not a v6.  Second, I don't think I
would consider adding a device to dramatically increase power output on
an eleven year old car that likely has milage close to 200,000.  You
may find that the old engine and transmission will wear out very
quickly as a result.

But check with the guys at swedespeed.com for details on superchargers
vs turbo's.  My tendency would be to pick the supercharger because
installation should be simpler.