Dream Theater has sold over two million albums in the United States alone and over ten million albums around the world, thanks to astoundingly important records like Metropolis Pt. 2: Scenes from a Memory (1999) and Systematic Chaos (2007). Sharing stages with musical titans Deep Purple, Iron Maiden, Porcupine Tree, Megadeth and Emerson, Lake & Palmer (to name a few) has contributed to the rightful perception of Dream Theater as one of rock’s greatest live acts.