If NRG Energy Inc. (NYSE: NRG ) were an athletic prospect, scouts would rate it as a “triple threat.” That’s because the Princeton-based wholesale power generator is involved in all three of the key energy sources of the future: Solar, wind and nuclear. And that’s only part of the reason I like this stock. Growing profit margins and earnings momentum add to the energy company’s appeal – and a rebound in U.S. economic activity hasn’t even begun in full. When NRG announced its second-quar