The redesigned Acura RL squeaks out a victory as best midsize luxury sedan.

Not long ago the BMW 5-series sedan seemed to live in a class by itself, defining the market for sporty, midsize luxury sedans priced above $40,000. It was hailed as a benchmark, the target rivals intended to hit with their cars — someday. Now, to paraphrase BMW's recent advertising, someday has arrived.

The 2005 Audi A6, Cadillac STS and Acura RL are all solid, well-engineered automobiles. They each offer more standard horsepower than the BMW 530i, yet two of them start off at a lower base price for six cylinders than the Bimmer. The critical differences: how their technology is presented to the driver and the elemental issue of bang for the buck. Below, we judge how these three newcomers stack up against the benchmark BMW, which we reviewed last December.

Audi A6
The other cars in this category try very hard to be guy cars. The A6 is more metrosexual — smoother and rounder on the outside and plush on the inside.

I drove the V-8 version, the 4.2 with Quattro all-wheel drive, which starts at $51,220 (all prices include destination charge). Equipped with XM Satellite Radio, a navigation system and other options, my test car stickered at $56,920. The new 3.2 Quattro model, which uses a new 255-hp V-6, starts at $41,620. Loaded with options, it can easily cruise past $47,000.

The new A6 has lots of good points. The ride is not too stiff, not too soft. The car offers a full array of safety technology and remains a good value compared with the BMW. But the Audi annoys where it shouldn't. The six-CD changer is in the glove box, and operating the control knob that works the radio, climate control and navigation system is not very intuitive.

Cadillac STS
If you wrote off Cadillac years ago, the 2005 STS is going to come as a shock. The new STS is a serious contender that in certain ways — notably, the simplicity of its cockpit controls — is superior to the BMW 5-series. In other ways, including ride and handling, the new rear-wheel-drive STS runs right with the BMW.

The new STS comes with either a 255-hp V-6 or a 320-hp V-8. Among the technological options, there's a magnetic-ride system that responds to jolts and dips by activating magnetic fields in special dampers that keep the car steady.

On the road, the steering is firm, the body stable in tight turns. But to get goodies like satellite radio, you need the "luxury performance package," which totals $49,710 for the V-6. There's no all-wheel drive available on the V-6 until 2006. A loaded V-8 with all-wheel drive runs just over $65,000.

The STS is well worth a look. Still, the failure to offer all-wheel drive in the six-cylinder drops the STS to second in this race. It's a mistake Cadillac plans to correct.

Acura RL
The new RL's V-6 is rated at 300 hp — within sight of competitors' V-8s and far outpointing the BMW 530i. Yet on the road, the RL is remarkably quiet.

The 2005 RL also comes standard with a new all-wheel-drive system that can vary the torque directed to the left and right rear wheels. In a tight corner, the system shifts more torque to the outside rear wheel, which has the effect of pushing the car around a turn without understeer or oversteer.

Standard on the new RL are other features that are options on competing cars — such as XM Satellite Radio and a navigation system with real-time traffic alerts for 20 major cities. The Acura RL wins by a nose because it offers more for the money than the two V-6-powered rivals and sales in this segment are predominantly V-6 cars.

As for the BMW 530i, it is an excellent car, but the gap that used to separate BMW from most rivals in this class has all but vanished.