2.0L turbocharged DOHC I-4 (A3)

200 hp/207 lb.-ft.

+ Pumping power for its size

- A little fizzy at the top end

= Proof that downsizing works

4.2L DOHC V-8 (S5)

354 hp/325 lb.-ft.

+ Only Ferrari makes a better V-8

- Gas-guzzler tax hurts on a coupe

= James Bond of engines