Cadillac's XTS full-size luxury sedan is entering its second model year—with some new high-tech options and a more powerful engine available. And no, it's not in the form of a V-8. Yet it should be just as good, if not better, than one. The new 3.6-liter Twin-Turbo V-6 that's available in the 2014 Cadillac XTS makes 410 horsepower and 369...