Sirius XM Radio (Nasdaq: SIRI) is doing better than you might think. The satellite-radio giant closed out the second quarter with impressive subscriber numbers and is increasing some aspects of its guidance for 2012.

Sirius XM tacked on 622,042 net subscribers during the second quarter, and that's impressive given the rate increase that the media titan initiated earlier this year. As a result of the strong showing, the company is now expecting to close out the year with nearly 1.6 million subscribers. Its previous outlook was for the addition of just 1.3 million net accounts in 2012.

Bulls will argue that the new guidance is still laughably conservative. Sirius XM has grown its rolls by more than a million subs during the first half of the year alone. However, CEO Mel Karmazin's knack for offering up guidance that can easily be revised higher has helped make Sirius XM one of the market's hottest investments since bottoming out a little more than three years ago.

Sirius XM is also increasing its top-line outlook. Karmazin expects revenue to approach $3.4 billion this year, just ahead of the earlier $3.3 billion target. The adjusted EBITDA and free cash flow guidance remain at $875 million and $700 million, respectively.

Most bulls aren't surprised.

"Sirius XM reports in a few weeks, and there's always the possibility that it can preannounce good news if it wants to revise its guidance higher or spill the beans on how many subscribers it has tacked on over the past three months," I wrote last week.

Sirius XM now has 22.9 million subscribers in North America, beating DirecTV (NYSE: DTV) with less than 20 million to be the top dog among satellite subscription services. Sure, satellite-television customers pay a lot more for their programming than premium radio buffs shell out. DirecTV also has another 8.5 million accounts in Latin America, outside Sirius XM's reach. But it's still an impressive feat for a company that was on the brink of bankruptcy three years ago.

We'll find out more information when Sirius XM reports its final quarterly results on Aug. 7. The only downside to the preannouncement is that the actual earnings report may be a bit of a letdown. We've seen this happen before with Sirius XM. Karmazin spills the juiciest news a few weeks before the actual report to keep the bulls happy, even if it means fewer fireworks when the quarterly results are unveiled.

This could very well be a tactical move to keep its stock buoyant this time, making sure that Liberty Media (Nasdaq: LMCA) pays up if it wants to continue to add to its mounting stake in the satellite-radio star.

This is a gripping soap opera, and all that investors need to know now is that Sirius XM is reaching a lot of more ears -- and pocketbooks -- than the market was expecting. 

Running of the bulls
I remain bullish on Sirius XM's future. It should come as no surprise that I'm promoting the CAPScall initiative for accountability by reiterating my bullish call on Sirius XM for Motley Fool CAPS.

XM Satellite Radio was a Rule Breakers recommendation before the Sirius XM merger. It's now gone from the scorecard, but if you want to discover the newsletter service's next Rule-Breaking multibagger, a free report reveals all.