Heady growth while keeping costs in check? Are we really talking about Sirius (NASDAQ:SIRI)? We are. The country's fastest-growing satellite radio service produced third-quarter results that found the top line soaring 150% higher to $167 million as subscriber acquisition costs and overall deficit narrowed.

Losing $163 million for the period isn't pretty, but it's better than the $180 million the company posted as a loss for the third quarter in 2005. Most notably, investors will remember this as the first quarter in the company's history in which total revenue was greater than the amount of its net loss. It's about time! It's also about to get even better.

Subscriber acquisition costs per gross addition fell from $149 last year to $119 for the period. It may sound like a lot, but it's not much more than what the company is getting in upfront money from new subscribers who pay months -- if not years -- in advance. Two months ago, CFO David Frear noted that the difference "will likely be zero or positive as we move into 2007." As it stands, the company is looking for that cost metric to fall to $110 in the current quarter.

CEO Mel Karmazin is still targeting positive operating cash flow before capital expenditures for the current quarter. Earlier this week, rival XM Satellite Radio (NASDAQ:XMSR) also pointed to this year's final quarter as a financial breakthrough period.

The holiday quarter will also likely find Sirius gaining more net new subscribers than XM for a fifth consecutive quarter. Sirius expects to nab 1.2 million net new subscribers to close out the year at 6.3 million. XM is still looking to close out the year with more accounts -- between 7.7 million and 7.9 million listeners -- but that implies that XM will land no more than 0.7 million net new subscriptions.

It's no longer just about satellite radio, of course. Both XM and Sirius have been successful in launching Internet streaming services, as well as premium music offerings for cell phone users. As long as subscribers keep coming and losses keep narrowing, it's a snappy tune that shareholders won't mind singing along to.

Check out what executives at both XM and Sirius had to say back in September:

XM is an active Rule Breakers newsletter recommendation.

Longtime Fool contributor Rick Munarriz is a Sirius and XM subscriber. He is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. He does not own shares in any of the companies in this story. T he Fool has a disclosure policy.