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.

Ball Corp. ( BLL) manufactures metal and plastic packaging.

The numbers: Second-quarter net income increased 33% to $133 million, or $1.40 a share. Revenue declined 7% to $1.9 billion. Its gross margin rose from 16% to 17% and its operating margin climbed from 9% to 10%. A quick ratio of 0.5 demonstrates weak liquidity. A debt-to-equity ratio of 1.8 indicates excessive leverage.

The stock: Ball Corp. is up 26% this year, beating the Dow and S&P 500. The stock trades at a price-to-earnings ratio of 15, a discount to the market and container peers. The shares offer a 0.8% dividend yield.

Dollar Tree ( DLTR) operates discount variety stores.

The numbers: Second-quarter profit surged 51% to $57 million, or 63 cents a share, as revenue jumped 12% to $1.2 billion. Its gross margin rose from 37% to 38% and its operating margin increased from 6% to 7%. A quick ratio of 0.8 indicates less-than-ideal liquidity. A debt-to-equity ratio of 0.2 reflects fiscal prudence.

The stock: Dollar Tree has advanced 18% this year, more than the Dow, but less than the S&P 500. The stock trades at a price-to-earnings ratio of 17, a discount to the market and general merchandise peers. The company doesn't pay dividends.

Sykes ( SYKE) provides customer contact services.

The numbers: Second-quarter profit decreased 19% to $14 million, or 35 cents a share, as revenue grew marginally to $209 million. Its gross margin was unchanged at 39% and its operating margin rose from 8% to 9%. The company has an ideal financial position, with $239 million of cash and no debt.

The stock: Sykes is up 27% this year, beating the Dow and S&P 500. The stock trades at a price-to-earnings ratio of 18, a discount to the market and office service peers. The company doesn't pay dividends.

-- Reported by Jake Lynch in Boston.

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