You can tell there is something interesting under the silver hood when you turn the key.

The engine turns over quickly, with a slight supercharger whine at start-up, before a menacing-if-mellow burble comes from the quad tailpipes.

The E55 is Mercedes-Benz's new family supercar, retuning its two-year-old mild-mannered E-Class sedan into a 469-hp wundercar that can handle four adults in comfort and safety at speeds far beyond what the highway patrol ever wants to see.

Do you really need a sports sedan that starts at ,650 and lists for ,985 as tested?

No.

Do you want one?

Let's see.

Mercedes began selling more powerful versions of its standard models through its European dealerships in 1993, using an independent developer of high-performance and racing cars cars known as AMG. The last-generation E-Class Mercedes received the AMG touch in 1999. Nicknamed the Hammer, its hand-built 349-hp, 5.5-liter V-8 engine helped it get to 60 mph in 5.4 seconds. Mercedes bought a majority interest in AMG in 1998, and will become the outright owner by 2009. Now any Benz bearing the AMG gets an engine hand-assembled by one of 62 specialists at a factory in Affalterbach, Germany, identified with a plate containing the signature of the technician who built it.

The E55 we tested is a modification of the 2003 E320 and E500 midsize sedans, its swoopier shape receiving some subtled muscling up, starting with a larger front air intake with black mesh grille and aggressive lower front air dam under distinctive Bi-xenon headlights.

AMG design also added sculpted side skirts, which visually lower the car as it sits on AMG 18-inch 10-spoke aluminum-alloy wheels wearing Pirelli Sport-Contac P245/40 ZR18-inch rubber in front and larger, lower-profile P265/35 ZR18 rubber in back. It also gets an aluminum trunklid, hood, front fenders, front subframe and crossmember, rear parcel shelf and rear wall behind the rear backrest. Subtle V-8 Kompressor badges are here and there, while the rear, big chromed double-twin exhaust tailpipes that project from a gray lower valance are a real giveaway.

Thanks to a suspension that can hunker the car down lower for higher-speed work, the effect is of a hunkered-down that means business.

Inside, the redesign has more curves than previous, somewhat staid Benz dashes. Gray-over-blue AMG Nappa/Nubuck leather upholstery swathes the seats and door panels, while a slash of birds-eye maple trims the dash, console and door panels, with AMG logos on the door sill plates and seat backs. A discrete chrome strip joins the wood trim to brighten things up.

The seats were superb, comfortable and very supportive. They have 10-way power adjustability, four individually inflatable air cushions for variable lumbar, lateral and thigh support, a lower back massage and five small fans per front seat that draw air off your back and and cool you down, if you don't need heat. A myriad of buttons under your thighs operate those and the Driving Dynamic system, where air bladders inflate or deflate automatically to bolster you in turns. The 17-button, dual-zone climate control system under the center air vents cooled the passengers fine on hot days.

A floating needle tells speed on the white-faced central 160-mph speedometer, flanked with an AMG-badged clock on the left and 7,000-rpm tach on the right, with digital bar-graph temperature and gas gauges. The power tilt/telescope AMG sport steering wheel in front of it receives power tilt and telescope adjustment, with up-shift and downshift gearshift buttons under the top spokes, and controls for the multifunction (trip odometer, fuel range, radio frequencies, diagnostic fault messages, clock, outside temperature, turn-by-turn navigation instructions) dashboard display in the speedometer center.

The main Cockpit Management and Data (COMAND) system's 6.5-inch color display screen in the dash center displays satellite navigation, stereo and other information with the use of 42 dials and buttons that surround it. Or move it upward at the touch of a chrome button to reveal the 12-speaker, 420-watt AM-FM-weather band stereo's six-disc CD player, which sounded superb.

The optional Panorama sunroof offers smoked glass panels over front and rear seats, with power shades that let the sun shine in. The DISTRONIC cruise control was cool, too, a radar system allowing the driver to pre-set the distance the E55 should maintain from the car in front at any speed, and even applying up to 20 percent brakes if the car ahead slows down or cuts you off. And if the radar sense an immovable object, a red triangle flashes accompanied by a beep to remind you to brake.

Back-seat room is decent for two adults, with sculpted leather seats with center armrest with cup holders, although there wasn't a lot of room under the front seat for feet. And the back panel of the driver's seat fell off late in the test, revealing wires, pumps, fans and other stuff . The trunk is huge, and opens at the touch of a button, as well as motoring closed.

So how does the E55 match with its E500 predecessor, which had 302 hp and 339 pound-foot of peak torque and took us to 60 mph in six seconds? The E55's 5.5-liter V-8, with 469 hp and a massive 516 pound-feet, rocketed to 60-mph in 4.7 seconds, with tire squeal in first and second gear followed by abrupt traction control activation as it shoved us in our seats. The 400-hp Cadillac CTS-V did the same in 4.8 seconds with rear axle hop. It costs about ,000 less, and can be had with a six-speed manual, although you can shift the E55's smooth five-speed automatic via soft-touch alloy buttons under the steering wheel, or slapping the gearshift left and right. And leave the traction control on -- this baby will burn rubber any time you want. Even with spirited use, we managed an average 18.5-mpg on premium gas.

But like a German nanny, you many times know who is in control of this car -- the computers.

The AIRmatic DC suspension and Adaptive Damping System allows a computer to monitor road conditions and set the computer-controlled springing and damping appropriately via rubber bellows inflated or deflated by compressors to vary the springing rate from maximum comfort to sporty. It worked, offering a supple yet controlled ride on its base setting, or a firm-yet-controlled ride with more compression and maximum damping stiffness during spirited driving. It was never harsh, and almost all body lean was gone in hard cornering as it securely carved its way around any turn. The rear end stays admirably in control in turns, the E55 understeering a bit if pushed. And even with the electronic stability control shut off, it still kicks in a bit if you try to hang the catchable tail off. It's fun, but always under control.

The power steering felt precise, but lacking in a more precise feel I would have liked with this car, and a bit more feel in turns. The drive-by-wire braking system is connected to huge 14.2-inch front discs and 13-inch rear discs in back. It halted the car on a proverbial dime from 60-mph time and time again without fade or any real nose dive, but pedal feel was a bit artificial, so the brakes seemed to engage abruptly even after days of familiarity.

The E500 sedan we tested a year ago cost a bit more than ,000 as optioned. The E55 has a base price of ,650, including a 469-hp V-8, leather and wood interior, AM-FM-six-disc CD stereo with surround sound, high-performance brakes and tires, dual front air bags with front and rear side air bags and head-curtain air bags and alarm, electronic stability control. Options add the bling, with a ,595 hands-free telephone, ,010 DISTRONIC cruise control, ,530 Panorama sunroof, ,200 COMAND system, rear power window shade, CD changer and power trunk closer. Add the ,050 comfort package with air conditioned front seats, the ,180 Bi-Xenon headlights with washers and a destination and gas guzzler tax, and the manufacturer's suggested retail price is ,985.

That's a lot of cash for a lot of power, comfort and security for four, with a wee bit too much technology babysitting you. But this is the car you may want for a fast-car foursome some day.