When Sirius Radio (NASDAQ: SIRI) bought and closed in on rival XM Radio last month, the first thing Sirius CEO Mel Karmazin did was to look at cost cutting via taking out redundancies from the merged company. Although all kinds of ideas are floating in the air to increase Sirius subscriptions and push its stock price back above the $1 mark, some are questioning how the combined satellite radio company can grow in 2009.

Indeed, Sirius estimated its subscriber base this morning to be at 19.5 million paying subscribers by the end of this year, with growth hitting 21.5 million subscribers by the end of 2009. So, that leaves Sirius with a goal of growing its base two million subscribers next year. Analysts noted that those numbers are a slowdown from 2007's addition of 3.7 million subscribers and 2006's addition of 4.4 million subscribers. Of course, there were two companies offering service those two years -- now there is one.

Unless Sirius can be really aggressive in marketing its aftermarket radios in new vehicles (the subcompact, four-cylinder kind consumers are actually buying) and ensure Sirius radios are offered as standard equipment in the vehicle product mix outside the defunct truck and SUV markets, it will have a tough time hitting 2009 prospects for growth. There are simply too many other alternatives for consumers listening in their cars (iPods and podcasts/downloaded music, anyone?). Karmazin's constant explanation during the XM merger process was that consumers have so much choice about what to listen to and where, that a combined Sirius/XM would not be a monopoly threat. He's right, and it's starting to show as subscriber numbers slow down.