The S&P 500 index had a great month, surging 3.5%. But these stocks soared much more.The S&P 500 index of 500 of America's biggest companies gained a solid 3.5% in September -- its fifth consecutive monthly gain. If 3.5% doesn't seem like a lot, remember that it's just a month's gain. (For comparison, it gained 1.9% in August.) If it were to rise 3.5% every month, that would compound to an incredible 51% annual gain.The top-performing stocks of the month were Warner Brothers Discovery (WBD -0.62%), AppLovin ...