LONDON — Audi has released official prices on the U.K. edition of the redesigned S4. When the cars go on sale in Britain in April, the S4 sedan will start at $50,800, and the S4 Avant wagon will be priced from $53,200.Only the S4 sedan will make the transatlantic trek. It is expected to go on sale in September as a 2010 model, also priced from around $50,000.The supercharged 3.0-liter TFSI V6 in the new S4 is rated at 328 horsepower and 325 pound-feet of torque. U.K. customers can order either model with the optional Audi S tronic seven-speed twin-clutch DSG transmission, priced from $1,800 to $2,100.The new S4 will jet from zero to 60 mph in less than 5.1 seconds. Top speed will be electronically limited to 155 mph.In the U.S., the current S4 Sedan 4.2 is priced starting at $49,385.Inside Line says: The new S4 gets a much-smaller-displacement engine with fewer cylinders, but boasts a better acceleration time and superior mileage. Not a bad trade-off. — Paul Lienert, Correspondent