XM Satellite Radio and Sirius Satellite Radio said Tuesday they have completed their long-pending merger. In this March 20, 2008 file photo, a sign for XM Satellite Radio hangs over its exhibit space at the New York International Auto Show in New York. Federal regulators formally approved the merger of the nation's only two satellite radio operators Friday, ending a 16-month-long drama closely watched by Washington and Wall Street. Sirius Satellite Radio Inc.'s $3.3 billion buyout of rival XM Satellite Radio Holdings Inc. will mean 18 million-plus subscribers will be able to receive programming from both services. ...