With the 2004 introduction of the QX56, Infiniti decided to make its own mark on the full-size luxury SUV segment with a powerful and luxurious sport-ute of its own. "Q" has long been the letter to signify Infiniti's top models, namely the Q45 sedan, while the "X" stands for sport-utility. Finally, "56" denotes the SUV's 5.6-liter engine.

Looking at the QX56's profile, it's obvious that it's based on the Nissan Armada. It's not uncommon for luxury SUVs to share a familial resemblance with lower-line siblings, but we find the Armada's styling, particularly the roof and side window design, a little bizarre. With a curb weight of about 5,600 pounds, the QX56 needs some serious oomph to move it out, and fortunately it's got it. Displacing 5.6 liters, the 32-valve V8 pumps out 315 horsepower and 390 pound-feet of torque -- more than enough to make the heavyweight Infiniti QX56 feel light on its 18-inch tires. Both rear-wheel-drive (2WD) and four-wheel-drive (4WD) configurations are available. With a maximum tow rating of 9,000 pounds, the Infiniti SUV probably has more capacity than 90 percent of its owners will ever need.

With the interior of the Infiniti QX56, it's obvious that Infiniti attempted to turn a sow's ear (a.k.a. the Armada's interior) into a silk purse. The results are a mixed bag; the leather upholstery, beautiful wood trim and handsomely stitched and well-padded armrests boost the luxury quotient considerably over the bland Armada's. And both the first- and second-row seats are heated. But some low-grade components, notably the dull gauge cluster and the hard plastic used on the doors and dash top, bring it down when compared to its more lavishly appointed competitors. Nevertheless, the QX56's plush leather seats are sure to be enjoyed by all, and there's enough legroom in the second row so that even 6-footers can get comfortable. For those who may need eight-passenger capacity, a second-row bench seat is a no-cost option in lieu of the standard captain's chairs.

With class-leading performance, massive towing capacity (nearly double that of the Lexus LX 470) and a roomy and comfortable cabin, the 2006 Infiniti QX56 certainly makes a strong case for itself in the practical sense. Its long-range success will depend on how many buyers in this prestige-oriented segment are willing to prioritize those attributes over less substantial ones such as flashy style and status-quo nameplates.

The Infiniti QX56 is a full-size luxury SUV that comes in one trim level with either two- or four-wheel drive. As expected, standard features are plentiful, including 18-inch chrome wheels, HID headlights, Bluetooth connectivity, leather seating for seven, real wood trim, a DVD-based navigation system, a 10-speaker Bose audio system, dual-zone automatic climate control, a separate rear air conditioner, one-touch power windows and a power rear liftgate. The short list of options includes a bench seat for the second row (increasing capacity to eight), satellite radio, a power sunroof and a very handy rear backup camera system packaged with adaptive cruse control.

Power comes by way of a 5.6-liter V8 with 315 hp and 390 lb-ft of torque. A five-speed automatic handles the shifting duties, sending the power to either the rear wheels or all four wheels via Infiniti's All-Mode all-wheel-drive system. Maximum towing capacity is 9,000 pounds with 2WD and 8,900 with 4WD.

Side curtain airbags offer protection to all three rows of passengers, and seat-mounted side-impact airbags protect front-seat passengers. A reverse-sensing system is standard, and a useful rear video camera is optional. All QX56s include four-wheel antilock disc brakes, traction and stability control and a tire-pressure monitor. Power-adjustable pedals help owners find an ideal driving position and are linked to the standard memory system. In NHTSA front-impact crash tests, the Infiniti QX56 earned a top five-star rating for its protection of front occupants.

Around town, the 2006 Infiniti QX56 moves out briskly and effortlessly storms up freeway on-ramps to blend into fast-moving traffic. The five-speed automatic provides seamless gear changes and steps down promptly when a burst of power is needed for quick passing. An independent suspension all around provides the well-damped ride quality that luxury SUV buyers would expect along with surprisingly nimble handling for a vehicle of its size. Body lean is noticeable when cornering, but it's nothing excessive -- just a reminder to the driver that in spite of the QX56's sure handling, there is still a lot of sheet metal getting tossed around.

The Infiniti QX56 interior is swathed in leather and thick carpeting. The steering wheel is trimmed in wood and aluminum, and the console features a generous plank of either dark Macore or blonde Apaya wood trim. Unfortunately, hard plastics on the dash and doors somewhat detract from the upscale ambience. Second-row captain's chairs are standard, along with a removable center console and third-row split fold-flat bench seat. A fold-flat second-row bench seat is optional. Big as it feels on the inside, the QX56 has less maximum cargo capacity than an Escalade or Navigator, with just over 97 cubic feet of space. But if you're planning to seat passengers in all three rows, the Infiniti SUV has the advantage, with a generous 20 cubic feet behind the third row.