Last month, green energy mogul Michael Polsky made a splash when he snapped up JP Morgan Chase CEO Jamie Dimon's 13,500 square-foot Gold Coast mansion (view photos here). Now, it's time to unload the home that he's been living in for the past six years. That modest abode happens to be a 4,150 square-foot penthouse in a River North building known as "Grand on Grand" (view photos here). Isn't that grand? That sounds like a pretty big step up, and indeed it is, but Polsky's penthouse is nothing to sneeze at. The full-floor 3BD, 3.5BA palace in the sky has a wood-paneled library, 13-foot ceilings and six balconies and terraces. According to Crain's, Polsky bought the place for $1.48 million in 2004, and he recently listed it for $2.6 million.