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MOUNT CLEMENS -- We didn't realize how much trouble we'd get Ken Madeleine into with his wife when we recruited him to help us test-drive the new 2006 Jeep Grand Cherokee SRT8 sport utility vehicle.

This Jeep is a landmark vehicle for the brand with lots of superlatives and firsts.

It's the most powerful Jeep ever built.

It's also the first four-wheel-drive model from SRT, short for Street and Racing Technology, Chrysler's high-performance arm, and the first Jeep ever to wear an SRT badge.

The Grand Cherokee SRT8 is powered by a 6.1-liter Hemi V8 that produces 415 horsepower and propels the SUV from zero-60 in less than 5 seconds. Think of it as Jeep's first true thrill ride.

We took the Detroit-built Grand Cherokee SRT8 over to the Madeleines' house because they own a 2004 Grand Cherokee, albeit one powered by a more modest 190-horsepower inline-six engine. Madeleine's wife, Debi, jumped in the back seat of the SRT8, and, with her husband behind the wheel, we headed out to Gratiot Avenue. He had barely made the first turn when the shrieking began.

"Ken!" Debi yelled. "What do you think you're doing? Don't get us killed."

"It's not me," her husband insisted, surprised by the Grand Cherokee SRT8's awesome power. "Gee, I barely touched the pedal."

Later, Madeleine, the principal of Fraser's Emerson Elementary School, would sum up his drive in the Grand Cherokee SRT8 this way: "It turns good men into bad boys." He was smiling when he said it.

It also does a number on their bank accounts. In other words, you will pay a price, in several different ways, for all of that terrific power and all-weather capability with the Grand Cherokee SRT8.

Our test vehicle, one of the most expensive Jeeps of all time, had a bottom line of $44,615, including a $695 destination charge.

It had three options, including a $1,200 GPS navigation system, $225 "inferno red" paint, and a $3,195 package that bundled items such as front and rear side-curtain air bags, rain-sensing windshield wipers, power adjustable pedals and heated front seats.

The Grand Cherokee SRT8's chief domestic competitor is the 2006 Chevrolet TrailBlazer SS, which is equipped with a Corvette-based LS2 6.0-liter V-8 engine that makes 395 horsepower. The Jeep's Hemi engine outguns what you get on the TrailBlazer SS - and has that "Hemi" name, which is especially popular among men. Note, the Jeep weighs 255 pounds more than the Chevrolet, so horsepower-to-weight ratios are pretty similar.

The Grand Cherokee SRT8's engine is mated to a five-speed automatic transmission while the TrailBlazer SS has a four-speed automatic transmission. But the Chevrolet returns better mileage.

The Grand Cherokee SRT8 is a classic gas-guzzler. The EPA says it gets 12 mpg in city driving and 15 mpg on the highway. Madeleine notes that's worse than the already dismal mileage he gets on his conventional Jeep -- 15 mpg in the city and 19 mpg on the highway. We averaged around 12 mpg during the week we tested the SRT8.

The TrailBlazer SS is rated by the EPA at 14 mpg city and 17 mpg highway.

In one respect, this Jeep stands head and shoulders above its crosstown rival: Price. Where the Grand Cherokee SRT8 starts at $39,995, the TrailBlazer SS starts at $27,199--nearly $13,000 less than the Jeep. Even loaded with options, the Chevrolet is thousands of dollars less.

The Grand Cherokee SRT8 has lots of things to recommend, however, from a firmer ride and reduced body movement versus the conventional model to exterior enhancements, including 20-inch five-spoke aluminum wheels and dual four-inch exhaust tips that look like they belong on the Batmobile.

But we came up with an equally long list of dislikes, including its impact harshness on rough pavement and uncomfortable, "performance" front bucket seats that felt like they were made for 17-year-old gymnasts with narrow hips.

We were also disappointed by the build quality of the cabin, something we suspect goes all the way back to the way the SUV was designed and doesn't just begin with issues at the factory. We noticed sloppy trim fits on the instrument panel, a gap at the top of the front pillar on the driver's side and little bits of flashing here and there that should have been cleaned up.

The view from the driver's seat is a bit disconcerting, too. You can't quite get the seat lowered enough to properly see out of the top of the windshield. This cuts off the view somewhat, especially at stop lights. And visibility is also impeded by the overly thick front pillars.

Little things also bugged us--like the tiny screen on the navigation system, which takes some serious squinting to decipher.

Still, the cabin is very attractive, in a racetrack kind of way, with faux carbon-fiber touches on the leather-wrapped steering wheel, instrument panel and shift knob. The gauges are striking, trimmed with blue accents. Those uncomfortable front seats do look nice, with suede inserts designed to grip occupants during aggressive maneuvering.

One of the best things about the Grand Cherokee SRT8 is how precisely it handles. The ride height is one inch lower than that of the standard Grand Cherokee, which adds to the vehicle's stability. The SRT suspension tuning makes it one of the more impressive SUVs we've driven. And it has such features as electronic stability program to help keep you firmly planted on the road when it's slippery, as well standard traction control and anti-lock brakes.

But the real appeal of the Grand Cherokee SRT8 -- as Ken Madeleine discovered -- lies under the hood. The big, brawny 6.1-liter Hemi sounds like a powerboat out of those massive tailpipes and leaps to life at the slightest twitch of the throttle. The 410 pounds-feet of torque that lurk under your right foot can be intimidating -- especially if you blip the accelerator right in the middle of a slow corner -- but the straight-line sensation of brute force and pure speed is exhilarating.

Let's put things in perspective. At the Essen Motor Show in Germany last week, the Porsche tuning house TechArt displayed a concept police car based on the 911, modified to produce 370 horsepower. With all that muscle on tap, the Porsche cop car will sprint from zero to 60 in around 4.5 seconds, which is just a tad quicker than the Grand Cherokee SRT8.