I have a 2000 XC and two months after I got it, the Angle(or Bevel) gear went south to the tune of $3100. Apparently, 8/32 of an inch difference between the front and rear tires in diameter is enough to break the angle gear, causing it to leak gear fluid, which has a very sick smell on hot transmission, and is not repairable. It is a unit which must be replaced. After I woke up from passing out at my repair bill, I got online and checked to see if I had been ripped off.
No, the XC for 1998, 99 and 2000 all have the angle gear, which Volvo abandoned for 2001 and went to a different design, because the angle gear is a flawed design. When they go out, you have to pay up for the new unit.
So if you want to pay big bucks for repairs, buy the 99 XC. The shocks are self leveling and are $300, just FYI. I'm upside down in what I have in my car, so I'm still driving it. But if I wanted AWD in a XC, I'd go with 2001 or later. No angle gear. It's your money.