Lee Richman installs high-end home theater systems that can cost as much as $170,000. Lately, he’s noticed that some of his clients — or their interior designers — are perking up when they hear about ultra-slim TV sets, which come off the wall only about an inch. The difference between these thin models and regular flat-panel TVs, which generally are about 3 or 4 inches deep, is pretty small. It’s nothing like the aesthetic shock that consumers had when flat panels were introduced to replace fat old cathode ray tube TVs.