The Infiniti’s luxury sedan comes in two models, the M37 and the M56. The first has a 3.7-litre V6 while the second has a 420-hp 5.6-litre V8. In both cases, there’s a seven-speed automatic transmission. Finally, these two versions are offered with rear-wheel or all-wheel drive. The Audi A6, BMW 5-Series and the Mercedes-Benz E-Class now have some competition! Totally redone this year, the M is an exquisite luxury performer.