It's the potent, powerful and - not to mention - pricey E Class avatar. A biturbo V8 engine that packs in 800 Nm of torque guarantees superlative performance. We test the car on the BIC track. Its big rival may well be the BMW M5, but in many ways the Audi S6 is also a competitor. With S6 too in the market now, we give it a test as well.