In a strong market for energy stocks, Southern Energy Inc. opened trading on the New York Stock Exchange Wednesday at $28�, up $6� over the $22/share offering price. Market observers expect an independent Southern Energy to generate better returns and puts the company on a more similar footing with firms such Enron Corp. and Dynegy Inc. in a deregulating energy market. Following the offering, Atlanta-based Southern Co. will continue to own about 80% of Southern Energy's stock.