NECESSITY may be the mother of invention, but nobody needed Volkswagen to develop a sleeker and lower version of its capable but dull mid-sized Passat sedan. Yet here it is anyway, the Passat CC 'Comfort Coupe', with four doors, four seats and one of the most powerful four-cylinder turbo-diesels available in base TDI guise. The thing is, VW has priced its BMW 3 Series competitor compellingly, packing it with features while matching and even exceeding many so-called luxury rivals for comfort and dynamic capability. So the question is: Do prestige sedan or coupe buyers actually need to consider the Passat CC TDI?