Sirius XM Satellite Radio is having its best day at market in recent memory thanks to a report claiming EchoStar has been buying up its maturing debt in preparation for an attempt to gain control of the company. Shares in Sirius are up more than 28 percent at 18 cents on The Wall Street Journal’s claim that EchoStar recently acquired part of a $300 million tranche of Sirius debt that matures on Feb.