XM Satellite Radio ( XMSR) was surging after a big research firm boosted its price target on the company's shares. Citigroup took its target up to $21 from $16, helping lift XM $1.11, or 7.3%, to $16.23. Citi reiterated a buy rating on the stock. XM has traded between $9.63 and $30.46 in the past year. Rival Sirius ( SIRI) was gaining 12 cents, or 3.2%, to $3.83.