TSC Ratings provides exclusive stock, ETF and mutual fund ratings and commentary based on award-winning, proprietary tools. Its "safety first" approach to investing aims to reduce risk while seeking solid outperformance on a total return basis.

TheStreet.com Ratings' model downgraded Blackstone Group ( BX) to "sell." The private-equity firm offers funds that invest in companies, real estate and hedge funds.

The numbers: First-quarter revenue fell 31% from a year earlier to $47 million as the company swung to a net loss of $231 million or 84 cents per share. Margins remained negative, but Blackstone's net loss declined from the fourth quarter. The cash balance improved 6.7% over last year's first quarter and the company reduced its debt burden 95% to $83 million.

The stock: Blackstone is up 34% this year after falling 70% in 2008. The stock offers a huge 13.7% dividend yield and management is confident about its ability to achieve a full payout in 2009.

The model downgraded BOK Financial ( BOKF) to "hold." The company provides money management and banking services.

The numbers: First-quarter revenue fell 9.7% to $358 million as net income and earnings per share declined 12% to $55 million and 81 cents, respectively. Operating margin improved 194 basis points to 36% and net margin fell 35 basis points to 15%. The company has $715 million of cash reserves, but a hefty $4.9 billion debt burden.

The stock: BOK Financial shares are down 12% this year, underperforming the Dow Jones Industrial Average and the S&P 500 Index. The stock has a price-to-earnings ratio of 16 and offers a 2.7% dividend yield.

The model upgraded Harbin Electric ( HRBN) to "buy." The company designs and produces electric motors in countries including China.

The numbers: First-quarter revenue climbed 37% to $30 million as net income increased 62% to $8.7 million and earnings per share improved 44% to 39 cents. Its operating margin shrank 12 percentage points to 26% and net margin declined 4 percentage points to 24%. The company has a low debt-to-equity ratio of 0.21 and a high quick ratio of 4.23, indicating ample liquidity.

The stock: Harbin Electric shares have surged 86% in 2009, outperforming all major U.S. indexes. The stock still trades at a low price-to-earnings ratio of 12, but doesn't pay dividends.

The model upgraded Louisiana Bancorp ( LABC) to "buy." This savings and loan company provides banking services in southern Louisiana.

The numbers: First-quarter revenue increased 14% to $4.5 million as net income increased 19% to $740,000 and earnings per share climbed 36% to 15 cents. Operating margin declined 94 basis points to 31% and net margin jumped 74 basis points to 17%. The company has a strong cash position, with $14 million of reserves compared with $64 million of debt. A debt-to-equity ratio of 0.79 indicates conservative leverage.

The stock: Louisiana Bancorp is up 4% in 2009, outperforming the Dow Jones Industrial Average and the S&P 500. The stock trades at a high price-to-earnings ratio of 25 and doesn't pay dividends.

The model upgraded NRG Energy ( NRG) to "buy." The company sells power it generates from natural gas, coal, wind and nuclear plants.

The numbers: First-quarter revenue increased 27% to $1.7 billion as net income quadrupled to $198 million and earnings per share surged 483% to 70 cents. Operating margin increased by 18 percentage points to 38% and net margin climbed 8 percentage points to 12%. The company's cash balance has almost tripled to $2.5 billion from a year earlier, but the firm still has a weak quick ratio of 0.5. The debt-to-equity ratio is higher-than-ideal at 1.03, but heavy debt is a common problem for utilities.

The stock: NRG Energy has gained 2% in 2009, outperforming the Dow Jones Industrial Average and the S&P 500. The stock trades at an extremely low price-to-earnings ratio of 6 and doesn't pay dividends.