Infiniti's got a whole new naming system-everything now begins with "Q"-and with it, some all new rides. First up: The Q50. The luxury sedan, set for unveil in Detroit in two weeks, replaces the current G Sedan. What's exciting? How about the potential of a Mercedes-Benz engine? That's right, the Q50 may be the first Infiniti to benefit from the cross-pollination of parent companies Nissan and the German giant.