Clock Ticks Slowly for XM, Sirius

As it stands, the two companies have incompatible technologies that would prevent current radios from receiving both satellite signals. Users will need to obtain new radios or some type of hardware upgrade to get combined programming.

On prices, Sirius CEO Mel Karmazin has said subscribers who already pay $13 a month won't have to pay more than $26 a month if they elect to get combined programming. Karmazin also said that the merged company could offer cheaper music-only packages and other discounts. He even welcomed regulators to apply price controls as "a way of holding our feet to the fire."

Still, the bigger hurdle for the merger lies with the Justice Department's antitrust lawyers. Washington legal experts say the deal hinges on what definition regulators apply to the satellite radio market.

A narrow view would show two satellite radio players becoming one and creating a monopoly. Antitrust lawyers would easily squash that deal. But the deal could proceed if the Justice Department considers iPods, conventional and digital radio, as well as Internet broadcasts, as part of the satellite-radio market.