Best Buy Profit Up, Backs Year Outlook  NEW YORK (Reuters) - Top U.S. electronics chain Best Buy  Co. Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=BBY.N target=/stocks/quickinfo/fullquote"&gt;BBY.N&lt;/A&gt; on Wednesday posted an 8 percent rise in  second-quarter net earnings on strong sales of higher-priced  digital products and curbs on expenses.