Not quite. XM didn't hit 6m until the first couple days of 06. They ended 05 with just over 5.9m.
Don't believe me?
"XM also had a record holiday selling season with more radios sold as Christmas gifts than ever before. More than 85 percent of XM's nearly 900,000 net new subscribers during the fourth quarter of 2005 came from retail sales. XM ended 2005 with 5,933,000 subscribers"