NEW YORK (

TheStreet

) --

Sirius XM

(SIRI) - Get Report

will celebrate reaching its

20 million subscriber mark

with an exclusive performance by Paul McCartney.

Sirius announced that it added 334,727 net subscribers in the

third quarter of 2010

, bringing the total number of subscribers to 19.9 million. The company expects to achieve the 20 million subscriber milestone shortly.

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"Reaching 20 million satellite radio subscribers is an important milestone for Sirius XM," president and chief content officer Scott Greenstein said.

Sirius and XM merged in 2008, and finished the year with a subscriber base of 19 million. That was up from 2007 when the companies had a combined 17.3 million subscribers, after breaking the 10 million mark in 2006 with a combined 13.7 subscribers.

Chief executive officer Mel Karmazin said he

expects approximately 20.1 million subscribers

by the end of the year, which would be the highest number of net subscribers in the company's history.

To celebrate, McCartney will perform at the Apollo Theater in an exclusive concert for Sirius XM listeners on December 13. McCartney will perform songs from his solo career, as well as songs he recorded with The Beatles.

"Sir Paul's performance at the Apollo Theater is our way of thanking our subscribers," Greenstein said. "We are thrilled to offer them an opportunity to attend the event and listen live to this once-in-a-lifetime concert on Sirius XM."

Sirius also announced it will launch a month-long music channel devoted to McCartney's expansive musical career called

Paul McCartney's Band on the Run Radio

. The commercial-free station will air from Nov. 29 through December 26 on Sirius channel 33 and XM channel 27.

-- Written by Theresa McCabe in Boston.

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