Deutsche Bank double downgraded Sirius XM to Sell from Buy with an unchanged price target of $6.25. The stock price has more than doubled over the past month and increased 42% yesterday alone, the analyst tells investors in a research note. The firm says this puts the stock 25% above its 12- month target. It believes the move higher has been driven by technical factors – very high short interest combined with buying ahead of the Nasdaq 100 rebalance after the close on July 21. Deutsche cites valuation for the double downgrade.