XM Satellite Radio surpassed 6 million subscribers, while rival Sirius Satellite Radio reached 3.3 million subscribers, triggering a $225 million stock payout to Howard Stern, the companies announced.

Washington-based XM added 2.7 million net new subscribers during 2005, finishing the year with 5.9 million subscribers, the company announced Jan. 4. That was short of XM’s goal of 6 million, but the company crossed that barrier early this year. XM attributed the lateness to radios purchased as Christmas gifts that were not activated until the first quarter of 2006.

XM said it expects to add 3 million net new subscribers in 2006, reaching 9 million by the end of the year.

New York-based Sirius saw its subscriber number jump 190 percent in 2005 to 3.3 million, the company announced Jan. 5. Sirius added 2.2 million subscribers during 2005 and expects to improve that pace and finish 2006 with 6 million subscribers.

Stern looks to be the biggest beneficiary of Sirius’ growth, as the company said it would transfer 34.4 million shares of stock to Stern and agent Don Buchwald Jan. 9, the day Stern begins broadcasting on the satellite radio provider. The stock transfer, valued at about $220 million, was triggered by the subscriber growth, an agreement Sirius and Stern reached in October 2004, Sirius said in a Jan. 5 filing with the U.S. Securities and Exchange Commission.