The Porsche Cayman--essentially a Boxster with a fixed roof--is the latest and greatest from Zuffenhausen, and although the differences between the Cayman and the Boxster are few, they are significant. The Boxster S's 3.2-liter flat six has been upped to 3.4 liters for duty in the Cayman S, and power has jumped accordingly to 295 hp and 255 lb-ft of torque, increases of 15 hp and 19 lb-ft. The Cayman also gets stiffer springs, thicker antiroll bars, different front-end styling, and new bodywork aft of the doors. The biggest difference, however, is in the driving. According to Porsche, the new steel roof doubles torsional rigidity; we can confirm that handling and chassis communication are better than ever. The highly capable car could easily handle 100 more hp; instead, a less powerful, non-S version arrives for 2007 at the 2006 Detroit auto show. PASM and PCCB--Porsche's cryptic descriptors for adjustable dampers and carbon composite brakes, respectively--are available, as is the Sport Chrono package, a favorite of track-day enthusiasts that was introduced last year on the 911 and the Boxster. A PASM-equipped Cayman S will cost thousands less than a base 911 Carrera, while nearly matching its 177-mph top speed and its 0-to-60-mph time of 4.8 seconds. (The Cayman S tops out at 171 mph and will reach 60 mph in 5.1 seconds.) The well-balanced Cayman is also more forgiving, more stable, more confidence-inspiring, easier to drive at the limit, and three seconds faster around the Nrburgring's Nordschleife. So the question is: Why buy a 911?