Bluetooth integration; steering-wheel and voice controls; keyless entry and ignition; crisp Multi-Media Interface display. The 2005 Audi A6 4.2 Quattro has the performance, the interior appointments, and the presence to hold its own against very capable and entrenched rivals. The 4.2-liter, aluminum-alloy 40-valve V-8 engine with variable intake-valve timing hustles the A6 along with alacrity. Fed through a six-speed automatic with Tiptronic manual control, the engine's 335 horsepower represents plenty of useful power. A sport mode moves upshift points slightly higher in the rev range, giving better acceleration when the need or desire arises.