The base engine on the 997 is the 3.6 liter flat 6. The S modes get the more powerful 3.8 liter flat 6. The X51 is a power kit factory add-on option that costs about $16,000.
The design on the Porsche 997 is about the same as any Porsche from the past 15 years, minus the SUV models. Some have criticized Porsche for making no effort to update their design for so long.
Porsche's performance numbers on the 997 seem to be a bit too conservative. An independent test carried out by some American car magazines showed that the Porsche 997 Turbo can go zero to 60 in about 3.4 seconds, which is right up there with any major production car in the world. These cars are very fast, and can keep up and often beat more expensive exotics from Ferrari and Lamborghini.
Whether you're looking to buy the Carrera, Cabriolet, Turbo, Targa, GT3, or GT2 version of the Porsche 997, the best deals you'll find are on eBay. That's right, the same place where you'd expect to buy vintage toys and baseball cards also has some great listings for exotic sports cars like Porsches and Lamborghinis.