BOSTON ( TheStreet) -- These companies have annual revenue above $500 million, below-average valuations, debt that is less than 49% of total capital and "buy" ratings from our 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. MGE Energy ( MGEE) is a Wisconsin-based electric utility. The numbers: Second-quarter net income dropped 6% to $10 million, or 43 cents a share. Revenue decreased 14% to $108 million. Its gross margin rose from 23% to 25% and its operating margin climbed from 15% to 16%. A quick ratio of 0.3 demonstrates weak liquidity. A debt-to-equity ratio of 0.7 is below the industry average, indicating restrained leverage. The stock: MGE has advanced 11% this year, less than the Dow Jones Industrial Average and S&P 500 Index. The stock trades at a price-to-earnings ratio of 16, a discount to the market and utility peers. The shares offer a 4% dividend yield. Casey's General Stores ( CASY) operates convenience stores in Midwestern states. 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 43% 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. The shares offer a 1% dividend yield.