Shares of Dollar General ( DG) were among the NYSE's winners Monday, soaring 27% after the retailer agreed to be acquired by Kohlberg Kravis Roberts for about $6.9 billion.

The private equity firm will pay $22 a share, representing a 31% premium to Dollar General's closing price of $16.78 on Friday. Including the assumption of debt, the deal is worth about $7.3 billion. The transaction is expected to close during the third quarter.

Shares of Dollar General were trading up $4.48 to $21.26. The deal sent shares of competitor Family Dollar Stores ( FDO) up 10% to $31.43, while Dollar Tree ( DLTR) was adding 80 cents, or 2.2%, to $36.46.

Sierra Health Systems ( SIE) surged 16% after the health care services company agreed to be acquired by UnitedHealth Group ( UNH) for about $2.6 billion in cash. The deal is worth $43.50 a share, representing a 21% premium over Sierra Health's closing price of $35.90 on Friday. The acquisition is expected to close by the end of 2007 or sooner. Shares of Sierra Health were up $5.63 to $41.53.

Shares of Spartech ( SEH) rose 8% after the plastics maker posted better-than-expected first-quarter earnings. For the period ended Feb. 3, the company earned $8.1 million, or 25 cents a share, on revenue of $347.3 million. Analysts polled by Thomson First Call expected earnings of 20 cents a share and a top line of $349.8 million. A year earlier, the company earned $5.7 million, or 18 cents a share, on revenue of $343.6 million.

For 2007, Spartech now sees earnings of $1.55 to $1.62 a share. Previously, the company predicted earnings of $1.55 to $1.60 a share. Analysts project earnings of $1.57 a share. Shares were adding $2.07 to $28.38.

Shares of Steel Dynamics ( STLD) rose modestly after the steel company boosted its first-quarter earnings forecast. The company now sees earnings of 94 cents to 98 cents a share, up from an earlier view of 85 cents to 90 cents a share. Analysts project earnings of 88 cents a share. The company said market conditions for flat-rolled steels have improved since mid-January. Shares were trading up 25 cents to $39.03.

Suntech Power Holdings ( STP) fell 5% after the maker of solar-power cells posted mixed fourth-quarter results. The company reported adjusted earnings of $35.5 million, or 23 cents a share, on revenue of $217.9 million. The bottom line topped analysts' expectation of 20 cents a share, but the revenue was shy of Wall Street's projection of $221.4 million. In the year-earlier quarter, Suntech recorded adjusted earnings of $16.8 million, or 13 cents a share, on revenue of $89 million.

Looking ahead, Suntech forecast first-quarter revenue of $220 million to $228 million. Analysts project revenue of $232.9 million. Shares were down $1.99 to $37.31.

Shares of Energy Partners ( EPL) traded actively after the oil and gas concern said that a review of strategic alternatives resulted in no definitive offers for the company to be acquired. Instead of a sale, the company plans to buy back up to 8.7 million of its shares, or 22% of its outstanding stock, in a tender offer of $23 a share. Energy Partners may repurchase another $50 million of stock following the conclusion of the current offer, which is valued at $200 million. Shares were trading down 8 cents to $17.92 on more than triple their average daily volume.

NYSE volume leaders included Motorola ( MOT), up 19 cents to $18.66; CVS ( CVS), down 51 cents to $32.09; Ford ( F), down 5 cents to $7.88; Caremark ( CMX), down $1.16 to $60.74; General Electric ( GE), down 13 cents to $34.19; Altria ( MO), up 14 cents to $87; Taiwan Semiconductor ( TSM), up 24 cents to $10.99; and EMC ( EMC), down 5 cents to $13.

Among Nasdaq's volume leaders were Sun Microsystems ( SUNW), up 6 cents to $6.33; Intel ( INTC), up 9 cents to $19.19; Level 3 Communications ( LVLT), down 1 cent to $6.31; Sirius Satellite Radio ( SIRI), down 2 cents to $3.40; Amgen ( AMGN), down $1.57 to $59.29; and Microsoft ( MSFT), down 4 cents to $27.25.

More from Investing

Interesting Symmetry but Strong Trends Are Likely to Give Way to Volatility

Interesting Symmetry but Strong Trends Are Likely to Give Way to Volatility

Investing Is a 'Constant Learning Game' According to M1 Finance CEO

Investing Is a 'Constant Learning Game' According to M1 Finance CEO

Johnson & Johnson Tops Q4 Earnings Estimate, Sees 2019 Sales Near $81 Billion

Johnson & Johnson Tops Q4 Earnings Estimate, Sees 2019 Sales Near $81 Billion

What Is Working Capital and How Do You Measure Assets?

What Is Working Capital and How Do You Measure Assets?

Analyst Predicts 'Buckle Your Seatbelt' Revenue Growth for iAnthus

Analyst Predicts 'Buckle Your Seatbelt' Revenue Growth for iAnthus