 Small-cap stocks have also historically outperformed large-caps as the economy has emerged from a recession, and building a portfolio of high-quality small-cap stocks during the current downturn could be a path to huge returns. With those points in mind, heres why investors seeking stocks capable of delivering explosive gains should add Glu Mobile NASDAQ: GLUU, Impinj NASDAQ: PI, and PROS Holdings NYSE: PRO to their portfolios. Lets take a closer look at these three top small-cap stocks to buy right now. 