Sirius XM (Nasdaq: SIRI) is one of the most volatile, heavily shorted stocks out there. Since its days as a penny stock to its eventual glorious resurgence, Sirius has taken investors on one heck of a ride. But things have since calmed down a bit for the satellite radio giant: Subscriber growth has taken off, churn is down, and the "Howard Stern question" has finally been put to rest.

Accordingly, the stock has gone up by 67% over the past year and is up 15% over just the past three months -- but how much further will it climb? Investors want to know what it will take for Sirius to hit the $2 mark, so we asked three of our Fool contributors that exact question.

Anders Bylund, Fool contributor
Can Sirius hit $2 per share? Sure it will.

Can Sirius stay above $2 for any length of time? That's the million-dollar question.

The stock is priced for perfection with a P/E ratio of 160 times trailing earnings and an enterprise value over 12 times trailing EBITDA. That's what the 6.9% short-sale cohort have seen and acted on. Satellite broadcasting rivals DirecTV (Nasdaq: DTV) and DISH Network (Nasdaq: DISH) look tremendously affordable by comparison.

Add in the fact that 65% of Sirius' shares are not owned by insiders, institutions, or other corporations, and you get one jumpy son of a gun. 

As long as Sirius executes flawlessly, everything is hunky-dory. But the first sign of weakness will bring terrible retribution from nervous shareholders. Howard Stern won't be a concern for the next five years, but is that enough to keep the ship on an even keel? I wouldn't bet the house on it.

Rick Aristotle Munarriz, Fool contributor
The easiest path to fresher highs may come from this year's rollout of Sirius XM 2.0. If the platform upgrade is revolutionary -- and not simply evolutionary -- investor excitement alone will get the stock above the magical $2 mark.

Dashboard tech is making great strides lately. Toyota's (NYSE: TM) new Entune multimedia system allows owners of Bluetooth-capable phones free access to Bing-powered navigation, the ability to snap up multiplex admissions through MovieTickets.com, and plan for dinner after the flick through OpenTable (Nasdaq: OPEN) restaurant reservations.

Will Sirius XM's new interactive platform raise the bar? As a premium service it doesn't have much of a choice. It will be competing against some pretty impressive automotive enhancements that carmakers are providing without monthly subscriptions in an effort to clear more cars off the showroom floor.

CEO Mel Karmazin hasn't revealed much of what the next generation of satrad receivers will do. We know that they're scheduled to hit the market during the fourth quarter, ahead of the holidays. Subscribers will also be able to access a broader range of content. Karmazin may be keeping mum on the exact specs to keep folks buying new receivers between now and then, but Sirius XM may also be tightlipped to make sure that the media giant can top everything else on the market.

The stock may blast through the $2 barrier before Sirius XM 2.0 hits the market. We have a couple of more quarterly reports to digest. Rival Pandora's IPO may draw attention to this niche. The heavily shorted shares are never too far away from a short squeeze if a magnetic celebrity signs a multiyear deal or a premium streaming service launches internationally.

Sirius XM is in better shape than bears think, and there are several roads leading to higher price points.

Tim Beyers, Fool contributor
Sirius XM has been treating me well. After years of skepticism, in October I called for a rally based partly on valuation and partly on a lack of institutional ownership. Sooner or later, I argued then, Big Money buyers would no longer be able to ignore Sirius' rebel yell. The stock is up 37% since, outpacing the S&P 500 by more than 25 percentage points.

Like many of Sirius' more passionate investors, I'm nowhere near ready to take profits. Why? The valuation doesn't justify a sale. Sirius trades for just 3.45 times its enterprise value when compared to revenue, a 16% premium to where it was when I first added the stock to my CAPS portfolio.

That the stock has risen much faster than the multiple tells me the business is improving structurally as revenue grows. And that, indeed, is the case: Returns on capital improved more than 46% year-over-year during the December quarter.

But I also like Sirius' subscription-driven model. Downloads make less sense in a market where broadband is becoming more pervasive, and in the process favoring streaming service providers such as Netflix (Nasdaq: NFLX), Akamai (Nasdaq: AKAM), and ... yep, Sirius XM. It's a virtuous development that means fewer satellites, fewer expenses, and a lot more profits.