The Russell 1000 Index posted a strong overall performance in Q3, closing the quarter up around 7%. However, the average stock returned about 4% which indicates that the largest gains were driven by a handful of high-flying names. Here's a look at the outperforming stocks that led the index in quarterly gains. QS stock is climbing. See the real-time price action here. Top Gainers Over 100%The Russell 1000 saw its best-performing stocks dominated by four standouts, which each gained over 100%. Sandisk Corp. ...