Audi RS6 (C5)
Why 5.7: 444 hp and 560 Nm in 2002 made this the most powerful Audi ever built at the time, and the first RS model exported to North America — as a saloon, where Europe also got the Avant. There was no manual gearbox, because no manual Audi had could take the torque.
Layout
Natural habitat
Ride comfort
Sound
The 4.2 biturbo is deep and enormously torquey, and on part throttle it makes a genuinely imposing low rumble. Two turbochargers and a refinement brief swallow the rest, and 6,800 rpm arrives with no change of register, which is rather the point of the car.
8-cylinder · turbocharged · 6,800 rpm redline · rated 5.5 / 10 for engine sound
Market value
Median asking price, good condition · €76k (2003) → €31k (2026), trending down · illustrative data
Child seats · ISOFIX
ISOFIX was spreading through these years rather than fitted across the board — whether a given car has rear anchors depends on its year and market.
Children were expected in the back. Front-passenger ISOFIX effectively didn't exist in this era, and airbag deactivation was patchy — treat the front seat as a no unless a specific car proves otherwise.
Derived from production years and seating layout, not a per-car source. ISOFIX was standardised as ISO 13216 in 1997, required on new EU model types from 2011 and on all new EU cars from 2014.
The long version
The C5 RS6 was assembled by quattro GmbH with Cosworth Technology's help on the 4.2-litre V8, which gained two turbochargers, new heads and 450 PS with 560 Nm from 1,950 rpm — the most powerful road car Audi had built. It also weighed 1,865 kg as an Avant and came only with a five-speed ZF Tiptronic automatic, because nothing in the parts bin would survive the torque with a clutch in it. What holds it together is Dynamic Ride Control, a system of diagonally cross-linked hydraulic dampers that resists roll and pitch without electronics; it works remarkably well and it leaks, and a full DRC replacement has written off a lot of these cars. This was the first RS Audi sold new in the United States, saloon only, roughly 1,200 of them for the 2003 model year. A 480 PS RS6 plus followed for Europe. Values collapsed to banger money by the mid-2010s and have only recently started back up, held down by the cost of everything underneath.