Enhanced technology is the cornerstone to luxury brand Mercedes-Benz's 2004 model year line-up. Introduced with an all-new sedan design for 2004, the E-Class' retouches have now been added to a wagon. For Mercedes-Benz SL-Class fans disappointed that the V-12 engined model wasn't available with the new model's introduction in 2003, 2004 marks the powerplant's return. Arriving as a turbocharged 5.5-liter V-12 with the 2004 Mercedes-Benz SL600, the model is propelled by 493 horsepower. A seven-speed automatic transmission is added to several Mercedes-Benz models for 2004. The E500, SL430, S500 and CL500 are recipients of the seven-gear transmission. Good and bad news is found with the Mercedes-Benz M-Class line for 2004. The base model receives a more potent 3.7-liter V-6 but the ML55 AMG model is discontinued. A special edition package is offered on the 2004 SLK230 and SLK320 adding unique exterior accents such as 17-inch wheels along with Nappa leather sport seats.