Consider the possibilities in this order: body style, engine, drive system and transmission. With the standard A4 sedans, think of Audi's popular quattro all-wheel drive system ($2,100 or $2,200, depending on the model) as an option. One of the two types of automatic transmissions ($1,200) can be considered as an option on most variants.

The A4 2.0T sedan ($28,240) is the least expensive model, powered by 200-hp, 2.0-liter turbocharged four-cylinder engine. The 2.0T Avant ($31,340) and other wagons come only with quattro, which is included in the price.

The standard upholstery is cloth, but the A4 2.0Ts come with lots of features, including dual-zone automatic climate control with cabin filtration, cruise control, tilt and telescoping steering wheel, power driver's seat, auto-on running lights, a 10-speaker stereo with six-CD changer and 16-inch aluminum wheels.

The A4 2.0Ts offer two option packages. The Premium Package ($1,900) includes a power glass sunroof and 17-inch wheels. The Convenience Package ($1,900) adds driver's seat position memory, Homelink remote transmitter, rain and light sensors, auto-dimming inside mirror with compass, auto-dimming and power folding outside mirrors and Bi-Xenon headlights with adaptive front lighting.

The A4 3.2 sedan ($35,540) comes standard with the CVT automatic, while the quattro models, including the 3.2 Avant ($37,440) offer the manual. Besides a 255-hp V6, the A4 3.2s add leather upholstery, sunroof and 17-inch wheels.

Additional option groupings for the A4 3.2 include a Cold Weather Package ($1,000) with heated seats and a ski sack, and Audi's S-line Sport Package ($2,750), which adds 18-inch wheels with performance or all-season tires, sport suspension, brushed aluminum trim and S-line styling tweaks.

Next up are the sport-tuned S4 sedan ($47,500) and Avant ($48,500), which feature a 340-hp 4.2-liter V8 and standard quattro. The S4s offer the DTM Appearance Package ($1,500), which is named for Germany's equivalent to NASCAR racing and includes carbon-fiber spoilers.

The A4 Cabriolet, or convertible, has only four seat belts, and is available in five models that roughly correspond to the sedans and wagons: 2.0T CVT ($39,100); 2.0T quattro with conventional automatic ($41,200); 3.2 quattro with automatic ($46,950); S4 manual ($55,700); and S4 automatic ($56,900).

The are lots of stand-alone options for all A4 and S4 models, including a navigation system ($2,100), a Bose stereo upgrade ($1,000) with XM satellite radio receiver, Parktronic distance warning ($350), special wood trim packages ($400) and headlight washers ($150).

The RS4 ($66,000) sits atop the entire lineup. This is a high-performance sedan of the first order, with a 420-hp 4.2-liter V8, manual transmission only and a special quattro system that biases power delivery to the rear wheels. It also includes most of the comfort and convenience features offered across the line.

Safety features that come standard include front-seat front and side-impact airbags, curtains-style head-protection airbags front and rear, and advanced, full-feature electronic stability and anti-lock braking systems (ABS). Rear-seat side airbags ($350) and a tire pressure monitor ($250) are optional.