The original SLK was the first car in its segment to feature the now-obligatory folding metal roof, and the current AMG model shows why it’s still so popular. As with the BMW Z4, buyers are actually getting a two-for-one deal—an urbane coupe and an equally refined convertible. And both are improbably fast, because shoehorned into the SLK’s stubby nose is AMG’s thundering 5.5-liter V-8, hooked up to Mercedes’ quick-thinking 7-speed automatic transmission. The hand-assembled unit pumps out a full-blooded 360 hp for devastating in-gear go that rockets the roadster deep into three-figure speeds. A raft of mechanical upgrades ensure that the rest of the package measures up—with its quicker steering, reinforced chassis, vast brakes, and upgraded suspension, the SLK feels alert and sharp on the move, thriving on fast, sweeping roads. It may be graying at the temples, but the SLK55 AMG still keeps up. Pros: The founding member of the folding-metal-roof club. Cons: The new Z4 is really, really good.