The A4 is Audi’s bread and butter. Now bigger than it used to be, this vehicle is offered in several different versions, including a conventional sedan with a 4-cylinder engine and the allroad wagon with its 8-speed Tiptronic transmission. Quattro allwheel drive is largely responsible for the A4’s commercial success. Performance buffs can always opt for the S4, which is equipped with a 333-hp V6 and a 7-speed manual transmission.