The 3.6-liter engine generates 255 horsepower, while the V8 produces 320 horsepower. The V6 does a more than adequate job of moving its 3,857-pound burden down the road. While the accompanying mechanical chorus from the V6 isn't as robust or viscerally satisfying as that from the V8, it's nothing to be ashamed of either.

The sportiest setup is the V8 with the optional performance handling package ($795). Nudging the shift lever over to the right, into the manu-matic gate where the selected gear will hold all the way up to redline, and thoughtfully alternating between the accelerator and brake pedal allow frolicing at extremes heretofore beyond the reach of sedans wearing the wreath and crest. Cadillac's suspension engineers have finally learned the difference between stiff and firm. Thankfully, all the sound filtering and deadening doesn't keep the V8's throaty exhaust note out of the cabin. Who needs a stereo with these tones to enjoy?

Then again, the all wheel-drive packaged with the Magnetic Ride Control supplementing the latest generation Stabilitrak is hard to top, though it adds some weight and isn't available with the handling package. Still, body lean in even the tightest switchbacks is almost non-existent, and mild whoop-de-doos barely give occupants' stomach a flip. Biasing 60 percent of the power to the rear wheels gives the all-wheel-drive STS the sporty dynamics of rear-wheel drive while sending enough power to the front wheels to pull the car through and out of corners with sureness and confidence.

The electronic steering is a delight, with the only shortcoming a slight softness on center. The car tracks well through corners, and turn-in is crisp, especially with the 18-inch, low-profile tires. The brakes are up to the car's potential, with a firm pedal and a feel that's more linear than not. Cadillac has ratcheted the Stabilitrak back a smidgen from its earlier aggressiveness, and it now waits a bit longer before stepping in. And when it does, it does so less abruptly, too.

The 3.6-liter V6 and the 4.6-liter V8 are GM's latest engines with double overhead cams, four valves per cylinder and variable-valve timing, or VVT. This latter system continuously varies valve operation to generate the most power from the least amount of fuel with the lowest emissions possible. Torque is what American drivers really use; torque is what gets a car moving in the first place, like when merging onto a freeway or passing on a two-lane. Recognizing that, Cadillac engineers designed the STS engines to generate lots of torque throughout the rev range for responsive performance at all engine speeds. The V6 gets a dual-stage intake manifold that makes available 90 percent of the engine's 252 pound-feet of torque from 1900 to 5800 rpm. The V8 uses electronic throttle, or drive-by-wire, to match the engine's performance to a variety of driver demands, from sedate interstate cruising to rambunctious backroad motoring. The V8 generates 315 pound-feet of torque at 4400 rpm.