The four-door coupe genre is all the rage and everyone from the big German trio has an offering in the segment. We check out a supercharged Audi S5 Sportback on the second-hand market, going for considerably less than what it did new.  What’s even more enticing is that it still has plenty of life left in the standard maintenance plan. Swift performance, sophisticated looks and a badge that will impress your peers. We get behind the wheel.