In addition to the satisfaction of a job well done, success also provides more tangible rewards, and few rewards are more gratifyingly tangible than climbing behind the wheel of a Mercedes-Benz E420 sedan. Or, for that matter, any member of the Mercedes E-Class lineup. While the pot of gold at the end of the fabled rainbow is questionable, there may very well be one of these. The Mercedes E-Class is comprised of three models. The least expensive of this trio (from $40,495, including destination charges) is the E300D, powered by a thrifty 3.0-liter six-cylinder diesel. The E320 (from $45,395) is the most popular member of the line, with a 217-hp 3.2-liter dohc 24-valve inline six-cylinder engine. The E420 tops the E-Class range, powered by a robust 4.2-liter dohc 32-valve V8 with 275 hp. With this kind of thrust, the senior E-Class entry rates as one of the planet's premier cabin-class hot rods. All three Benzes send their horsepower to the ground through an ultra-smooth five-speed automatic transmission driving the rear wheels.