Introduced midway through the third-generation 5 Series run in 2000, the M5 is as close to perfection as any ultrahigh-performance sedan has ever come. It's of course based on the 5 Series, specifically the 540i (already an incredible sport sedan in its own right) -- which BMW turned over to its Motorsport division for intensive powertrain and chassis modifications.

Starting with the 4.4-liter block from the 540i, BMW's M Division bumped displacement to 5.0 liters with a bore and stroke job. Compression is set at 11:1 (a full point higher than the 4.4-liter in the 540i), and the cylinder heads offer more efficient cross coolant flow and larger intake ports. Outfitted with Double VANOS steplessly variable valve timing, this engine is good with 394 horsepower at 6,600 rpm and 369 pound-feet of torque at a low 3,800 rpm. Even with the M5's curb weight of over 4,000 pounds, 0-to-60-mph acceleration happens in a lightning-quick 5 seconds. But don't expect those times to happen with both hands on the wheel; the M5's only transmission is a six-speed manual.

The M5's chassis is equally as dazzling as its drivetrain mechanicals. Mostly based on the 540i six-speed, the M5 has firmer shocks and springs and low-friction steel ball joints that replace rubber bushings at the outboard ends of the rear suspension's upper arms. The quick-ratio power steering has a 14.7:1 overall ratio and M Servotronic power assist. Compared to the engine-speed-sensitive variable assist of lesser 5 Series cars, the M5's system varies power assist according to vehicle speed. Large, fully ventilated disc brakes and 18-inch wheels wrapped in 245/40ZR18 rubber in the front and 275/35ZR18 meats in the rear complete the M5's handling package.

Put all the M5's awe-inspiring technical prowess together and you get a driving experience that's on the same level: awe-inspiring. While paying 75 large for a performance toy might not sit well with your more practical spouse, don't forget to mention all the luxury amenities that come standard on every 2003 BMW M5. Remember, you're not just buying a European hot rod, this midsize sedan is meant for safe and secure family transportation...right?

The 2003 BMW M5 is offered as a single model. Each one comes with 18-inch wheels wrapped in 245/40ZR18 rubber in the front and 275/35ZR18s in back; xenon headlights; leather upholstery; 16-way adjustable power, heated sport seats; a power tilt-telescoping steering wheel; a navigation system; a 10-speaker sound system with a trunk-mounted CD changer; dual-zone automatic climate control; one-touch windows; a moonroof and auto-dimming mirrors. Buyers can choose either aluminum or wood interior trim. Full maintenance is on the house for the first four years or 50,000 miles.

The short options list includes a premium M sound system (supplies a couple of subwoofers); front and rear parking sensors (Park Distance Control); folding rear seats; various sunshades; and a no-charge option to delete the rear spoiler.

While the basic architecture is similar to the 540i's 4.4-liter V8, the M5's larger-displacement 5.0-liter V8 is entirely unique. Using the hot rodder's magic dust that's known as stroking, the M5's engine has an increased stroke -- from 82.7 millimeters to 89 (or in standard terms 3.50 inches). Its 94-millimeter (3.70-inch) cylinder bores are also slightly larger compared to 92 millimeters in the 540i. Other changes include a higher compression ratio, redesigned cylinder heads, more aggressive cam profiles, a special induction system with eight individual electronically actuated throttle butterflies (one for each cylinder), a revised oiling system designed to cope with the rigors of extreme cornering and Double VANOS variable valve timing. The result is 394 horsepower at 6,600 rpm and 369 pound-feet of torque at a low 3,800 rpm. A Getrag six-speed manual with a heavy-duty clutch is the sole transmission choice.

Every M5 comes with large, four-wheel vented, antilock disc brakes; a sophisticated stability control system; front side-impact airbags and head protection airbags for front and rear occupants. Note that the 5 Series earned a "Good" rating in 40-mph offset crash testing by the IIHS.

Out on the road, the driving experience is nothing short of awe-inspiring. On deserted stretches of lonely two-lane, the 2003 BMW M5 is pure fantasy pulling up to and blasting through triple-digit speeds like a cheetah chasing down its prey. Massive amounts of big-block-style torque are available at any engine or vehicle speed, in any gear. Moreover, the sedan's chassis dynamics are equally enthralling. Over twisty back roads and hairpin curves, the M5 is simply infallible in its ability to go, stop, turn and grip. Despite its hefty curb weight, the M5 is as much at home on a racetrack as it is in the valet-park at any city's most exclusive watering hole.

The 2003 BMW M5 is every bit as luxurious as the 540i sedan on which it's based -- that means supple leather, warm wood inlays (or aluminum for those who want a more sporting ensemble) and high-quality materials everywhere else. The backseat offers seating for three, such that one could justify the M5 as a family car.