BOSTON ( TheStreet) -- The following companies have annual revenue of more than $500 million, below-average valuations, debt that is less than 49% of total capital and receive "buy" ratings from our proprietary quantitative model, which considers more than 60 factors. They're ordered by their potential to appreciate, starting with the company with the best growth prospects. Casey's General Stores ( CASY - Get Report) operates convenience stores in the Midwest. The numbers: Fiscal first-quarter revenue fell 24% to $1.2 billion, but profit grew 54% to $44 million, or 87 cents a share. Its gross margin rose from 13% to 19% and its operating margin jumped from 3% to 6%. The company has less-than-ideal liquidity, evident in its quick ratio of 0.8. But a debt-to-equity ratio of 0.2 indicates modest leverage. The stock: Casey's is up 41% this year, beating major U.S. indices. The stock trades at a price-to-earnings ratio of 16, a discount to the market and food retail peers. Shares pay a 1% dividend yield.