Back in the doghouse, Sirius XM Radio (Nasdaq: SIRI) shares have broken under the $1 barrier again.

The satellite-radio provider's stock ended yesterday's trading session at $0.95, its lowest close in nearly three months.

This isn't where longs figured they'd be after this past weekend's Russell index rebalancing, reintroducing Sirius XM to funds that track gauges pegged to the service's qualifying stocks. The stock has shed 13% of its value since the rebalancing.

Investors shouldn't take the dip personally, though. "If I can offer some words of encouragement to frustrated Sirius XM Radio investors, it would be this," I wrote two months ago. "It's not you. It's not the stock. It's the market."

Sirius XM isn't immune to the market's swings. If anything, it exaggerates them. It's a high-beta stock. Bulls can't expect much when equities are tanking. Bears can only kick themselves when Sirius XM goes along for the ride of the next market rally.

There have been some boldly bullish price projections lately. Satwaves' Brandon Matthews turned heads in May when he called a move to as high as $2 "very likely" heading into last week's Russell reconstitution. To be fair, he also warned of the likelihood of a pullback following the event.

Earlier this week, TheStreet.com's Alan Farley used technical analysis to make an argument for near-term strength in the stock, with a possible push up to $1.80 by year's end.

The bullish theories may seem flawed in retrospect, but they just didn't stand a chance once Mr. Market donned his sluggish bent.

It cuts both ways, of course. Sirius XM would never again trade as low as its $0.05 bottom once it became apparent that EchoStar (Nasdaq: SATS) and Liberty Capital (Nasdaq: LCAPA) were competing to step in as sugar daddies last year. However, Sirius XM's stock wouldn't be as high as it is today without the market rally that began in March of last year before fizzling out this past quarter.

Yes, Sirius XM's fundamentals have improved dramatically over the past year. It's profitable, growing, and raising its guidance. However, it's also simply marginally profitable and growing slowly.

Despite the technological sizzle and new car smell, analysts see Sirius XM's revenue growing just 7% next year, the same pace they expect out of satellite-television giants DirecTV (NYSE: DTV) and DISH Network (Nasdaq: DISH). Sirius XM already commands a valuation premium to those companies based on its enterprise value basis.

It's worthy of a premium. Margins should continue to improve as Sirius XM realizes more economies of scale and is able to get its programming costs in line. However, there's no point in having bulls or bears make price predictions in a vacuum. Sirius XM has proved its viability as a profitable business model, but that won't make it immune to climbing or sliding with the general market.

How big can Sirius XM eventually get? Share your thoughts in the comments box below.