YOUTH, that's what the Mercedes-Benz Sports Coupe is all about. The once staid Geman company's first three-door is firmly pitched at reducing the average age of its buyers. As is the motoring way in the 21st century, the Sports Coupe has a new look but shares its mechanicals with the popular C-class sedan. Initially, only the C200K was offered - that's a 2.0-litre supercharged version - although the normally-aspirated C180 (confusingly, a full 2.0-litre) went on sale early in 2002, crucially priced just under $50,000.