(MONEY Magazine) – These days a terrific new four-door sedan can be had for about $20,000. So if you're willing to spend double or even triple that, you have the right to expect a spacious head turner that can chauffeur the kids around in style and safety, help land you a prime space from the parking valet, and knock off 500 miles on a highway or back road without you or it breaking a sweat.

There's a name for this automotive triathlete: luxury sports sedan. Cars in this class promise a lot more than the prosaic family four-door, adding style and status along with amenities such as creamy leather, 22nd-century gizmos, and enough air bags to float the Goodyear blimp.

The very best of these vehicles add one more thing to the mix: the assurance that your big bucks were well spent. To find out which cars are worth your wallet, I assembled five of the newest combatants. I tested them on highways, New York City commutes and racecourses. I looked at performance (from accelerating to braking and the handling in between), luxury (features, ergonomics, driver and passenger comfort), design (exterior and interior styling, materials, fit and finish) and value (a lower price isn't enough; it's what you get for your dollar that counts), and rated each attribute on a 10-point scale. Adding up the scores for these categories produced one clear winner, one exceptional runner-up and--a few surprises.

ACURA RL Sibling Rivalry

PERFORMANCE 7 DESIGN 5 LUXURY 7 VALUE 6

On paper, the Acura RL looks like it should do well: It has more standard features than any car in this test, and Acura is known for building sporty, solid, near-luxury cars. But in this exclusive class, that Acura formula is less convincing.

First, the good stuff. The RL doesn't offer a V-8, but its 290-horsepower V-6 is the strongest six in the field. It's got a slick all-wheel-drive system that helps the car scoot around corners, fine steering and an excellent navigation system. The new optional Collision Mitigation Braking System actually brakes the car when it senses that you're not slowing down quickly enough to avoid an accident.

So what's the problem? Value. Another Acura, the TL, gives you nearly as much car for $15,000 less. There's no avoiding the comparison: The RL and TL are both built on the Honda Accord platform. The RL is a bit shorter, it's 430 pounds heavier, and it feels no roomier inside. The RL does add AWD, more features and 32 extra horsepower, but it lacks those luxury intangibles that would justify its price tag. The top finishers here reassure you that you're driving something special, yet the RL makes you feel like you're driving, well, a really nice Honda. As the final indignity, the TL is the better-looking car. The tentatively styled RL could be mistaken for a next-generation Accord--not good for a sedan with upper-crust aspirations. OVERALL SCORE: 25

LEXUS GS Too Smooth by Half

PERFORMANCE 5 DESIGN 8 LUXURY 8 VALUE 6

For more than a decade, the rap against Lexus has been that, in spite of peerless quality, its cars look like knockoffs of Benzes and BMWs. Fortunately, the latest GS sedan is a truly original design and the most striking of the Japanese entries. The GS' interior is up to the car maker's usual standard of excellence: Everything has a good solid feel, and the controls--except for a poorly situated fold-down panel by the steering wheel--are laid out in a clear, sensible fashion. (Lexus' touchscreen controls and navigation system are also among the easiest to master of any car's.)

Fitted with its optional V-8, the GS can cost a steep $60,000 or more, but keep in mind two things: Lexus offers the best reliability in the business and, as a result, bulletproof residuals. Those qualities can help soften the sticker shock.

When it comes to performance, the GS is comfortable, cathedral-quiet and quick, but Lexus still emphasizes plushness at the expense of handling. A true sports sedan has to have a little "sport" in it, along with a comfortable ride. The Lexus pampers, but at high speeds the car feels disconnected from the road, as if you're in a very accurate driving simulator. Lexus has mastered the luxury side of the equation, but it can't vie for top-dog status until it offers the whole package. OVERALL SCORE: 27

BMW 5-SERIES What Price Glory?

PERFORMANCE 10 DESIGN 7 LUXURY 8 VALUE 6

The 5-Series has taken hits for its adventurous styling, but that blue-and-white emblem still brings a lot of prestige to the table (which in turn keeps residuals high). There's little debate regarding the car's iDrive, however. Everyone hates this cumbersome console knob that controls things such as air conditioning and stereo settings. But ergonomic quirks aside, no other sedan combines such extraordinary agility and power with a smooth ride and hushed cabin.

That's especially true for the new 550i, with its 365-horsepower V-8 that reaches 60 miles per hour in 5.3 seconds. Six-cylinder engines in the 525i and the 530i are also unmatched for smoothness and efficiency. For purists, BMW offers both a manual shifter and a Formula One-inspired automated manual transmission with steering-wheel paddle shifts. Neither is available from competitors.

Yet despite its heady performance and best-in-class resale value, the 5-Series' price kicks it down to third place. Comparably equipped, the BMW is easily the most expensive car in this test. The base 215-hp 525i starts at more than $43,000; the 550i starts at around $58,000 and can soar above $70,000. The problem is that Audi's A6 is more luxurious and Infiniti's M sedan performs virtually as well--and each costs several thousand dollars less. OVERALL SCORE: 31

INFINITI M Power Trip

PERFORMANCE 10 DESIGN 6 LUXURY 8 VALUE 9

The M35 and M45 are roomy sedans that deliver BMW-like performance for less money. If not for a few luxury and design shortcomings, they'd be strong contenders for best in this class.

The M's exterior is hard to fault, but for such a high-powered sedan, it's also hard to get worked up about--there's little that's distinctive. Inside, Infiniti has raised its game with notably better materials and fit and finish, but there's a gimmicky center console laden with confusing and redundant switches. Where the Audi and Lexus cabins are both simple and elegant, the Infiniti feels like it's trying too hard.

Driving either M, however, is a gas. Their engines deliver explosive acceleration, especially the M45's 335-hp V-8. The steering provides excellent feedback; the suspension can handle the twistiest of back roads, though the ride isn't as smooth as that of some of the other cars. There's value here too: The V-6-powered M35 starts at a class-low $41,250. A nearly loaded M45 goes for around $57,000--that's $1,000 less than where BMW's 550i starts. That kind of performance and price makes the M a fantastic four-door. OVERALL SCORE: 33

AUDI A6 All the Right Moves

PERFORMANCE 8 DESIGN 10 LUXURY 9 VALUE 9

The A6 isn't as thrillingly sporty as the BMW or Infiniti, but for the money, it still proves to be the most complete luxury car.

While many automakers have been trying to get more "emotion" into their cars' contours (think strange angles and odd headlamp styles), Audi gave the A6 a subtle shape that looks gorgeous. The cabin is equally admirable. Everything looks and feels just right, cementing Audi's reputation for building some of the best interiors in the business. Even Audi's MMI controller is vastly superior to BMW's iDrive. In a nod to practicality, the A6 also has a cavernous trunk, the largest of all those we tested.

The A6 is also, no surprise, a pleasure to drive. It feels sporty on a back road and serene on the highway. Such all-around talent made it both entertaining and coddling on long drives.

The A6 is a top value, with a 255-hp, 3.2-liter front-wheel-drive model starting at $41,540. The 4.2 Quattro starts above $54,000, as it comes with a tremendous 335-hp V-8. The six-cylinder A6 is a smart buy: It will save you several thousand dollars and two to five miles a gallon without sacrificing performance.

The A6 combines progressive design and technology with traditional comforts. It's both sporty and comfortable. In other words, it's the essence of the modern luxury sports sedan. OVERALL SCORE: 36

The Specs

NOTES: [1] The A6 also comes with front-wheel drive. [2] Also available is the 530i, with a 250-hp, 3.0-liter, six-cylinder engine (19 mpg city/27 highway). SOURCE: The automakers.