Key TakeawaysShares of electric utility Vistra finished almost 6% higher on Wednesday, securing the strongest gain in the S&P 500.Vistra stock surpassed Nvidia earlier this week as the top-performing stock in the benchmark index year-to-date.Analysts at Jefferies and Morgan Stanley boosted their price targets for Vistra stock, citing optimism about data-center opportunities. Shares of Texas-based power generator Vistra (VST) surged nearly 6% higher on Wednesday, the largest daily gain of any S&P 500 stock. ...