I have a set of these in 19 inch they are replicas of the pegasus wheels fitted to the S60R they are a common wheel choice for modified volvos. Most people would try to steer you away from 20s. Volvo drivers wheel choices are usually limited to larger late model factory wheels.
Not many volvo drivers are throwing 20s on their cars as you have limited options with the factory pcd of 5x108 and a limit of around 8 inches in width.
this is taken from the ipd wheel fitment guide:
2001-2007 S60 can accept up up to a 235 section width tire a, common upgrades include 235-45-17", 235-40-18" and 235-35-19"