The Infiniti M is a luxurious four-door sport sedan, and it emphasizes a performance driving feel a bit more than some other cars in its class. Now badged the M37 (V-6), the M56 (V-8), or the M35h (Hybrid), the M sedans are all sized and priced to compete against the BMW 5-Series, Lexus GS, Jaguar XF, Acura RL, and Mercedes-Benz E-Class. For the...