Last December, the newly renamed Denver Museum of Nature and Science in City Park updated its 441-seat IMAX theater with a 15,000-watt (up from 8,500) digital sound system featuring six-track reproduction and -- count 'em -- 58 giant speakers. The sonic effect is rather like taking a front-row seat at the Battle of Verdun. There's also a brand-new screen -- four and a half stories tall, six and a half stories wide -- manufactured by the British firm Harkness. So if you're in the mood for a gigantic view of Dolphins, or some eye- and ear-popping Adventures in Wild California,or a trip to Cirque de Soleil: Journey of Man, IMAX is the place to be. All three films, shot in oversized 70 millimeter, are currently on view, a total of 35 times per week.