As XM and Sirius do battle for the hearts and ears of satellite radio subscribers, audience numbers are poised to take off, reaching 9.3 million by the end of this year - and growing nearly fourfold in the next five years - writes eMarketer, citing its Satellite Radio report, according to which 35.6 million Americans will subscribe to a satellite radio service by 2010.

The immediate question is "what Howard Stern's move to satellite radio will mean for his show, for Sirius and for satellite radio in general," says eMarketer editor and analyst Krikor Daglian, author of the report.

eMarketer estimates that the Howard Stern factor and a boost from holiday shopping will give Sirius over 3.2 million subscribers by the end of 2005. However, XM is expected to maintain its lead.

At the end of 3Q05, XM had over five million subscribers, up from 2.52 million a year earlier; Sirius had 2.17 million, up from 660,000.

The U.S. market is poised to nearly double from 2005 to 2007, when it is forecast to reach 19.0 million subscribers, reaching 24.2 million in 2008 and 29.2 million in 2009.