When the redesigned 2009 Mazda6 sedan goes on sale in late August, pricing will start at $18,550. The base Mazda6 i SV is fitted with a 2.5-liter, 170-horsepower I-4 engine and a six-speed manual transmission. At the other end of the range, the Mazda6 s with a 3.7-liter, 273-horsepower V6 engine and...