Nikada/E+ via Getty Images Following the S&P 500 and Dow Jones Industrial Average reaching new all-time highs, stock futures hovered near the flat line early Monday morning as investors eagerly awaited the next batch of key corporate earnings reports. Here are some of Monday's biggest stock movers: Biggest stock gainers SentinelOne (S) shares rose over 4% after Piper Sandler upgraded the stock to overweight from neutral, citing multiple catalysts that will boost shares through the end of the year. Analyst Rob Owens believes SentinelOne is gaining market share compared to CrowdStrike and that current estimates are too low for the next 18 months. With a price target of $32, Owens sees a 24% upside potential from the last closing price. B. Riley (RILY) shares soared 17% after announcing a $400M cash-and-stock deal to sell its Great American appraisal and valuations business to Oaktree Capital. Under the terms of the agreement, B. Riley will receive $203M in cash, $183M in preferred equity interest in a new holding company for Great American, and a minority stake in the holding company's common equity. Oaktree will acquire the majority of the common shares. The deal is anticipated to close by the end of the year. Sirius XM (SIRI) shares surged 9% after Warren Buffett's Berkshire Hathaway (BRK.A)(BRK.B) went on a buying spree in shares of the broadcasting and radio company earlier this week. The sprawling conglomerate purchased shares worth $86.73M in three separate transactions from October 9 to 11, boosting its total stake in the company to 108.72M shares.