Sirius XM CEO Mel Karmazin says, "We have added the last 10m subscribers faster than the first 10m - despite a tremendously competitive environment - representing a strong endorsement of our service and our programming by discerning consumers who want and demand the best in audio entertainment."

Back in October, the station upped its forecasts, projecting it would end the year with 20.1m subscribers.

Sirius and XM recently announced they will merge in Canada early next year. They currently operate ...