A $52,000 sport sedan. A $163,000 supercar.  Both worth every penny.

Aside from sharing an Audi badge and quattro all-wheel drive, the S4 sedan and R8 5.2 sports car might not seem to have much in common. Yet they do: Both models are so much more enjoyable than their basic versions -- the A4, Audi’s lowest-priced sedan, and the R8 with a smaller V8 engine -- that they become no-brainer choices for driving enthusiasts with sufficient means.

When I first encountered the V10-powered Audi R8 5.2 at Infineon Raceway in California's Napa Valley, and again over a week in New York, I was skeptical. The original R8, a midengine knockout with a 420-horsepower V8, was already a dream car, and already incredibly expensive at $115,000 to start. So even with the upgrade to a 525-horsepower V10 (a detuned version of the Lamborghini Gallardo’s engine) it seemed hard to justify a $32,000 jump in base price to $147,000. How much better could the R8 get?

            

Then I drove it. And in the time it took me to turn some laps at Infineon, my attitude was adjusted. Turns out that the V10 model is what the R8 was meant to be all along: a no-excuses exotic, with a top speed over 200 mph and the power, sound and exclusivity that six-figure buyers have a right to expect. As terrific as the standard R8 is to drive, its 420 horsepower puts you on par with a stock Corvette. The car needed more -- as in an additional 105 horses. If you can afford to drop 130 grand on an Audi sports car, you might as well spend 160 grand to have a car that can hang with any Porsche Turbo and feels as special as a Ferrari.

           

And for those of us in the real-world realm, there’s the Audi S4 (and its gorgeous S5 Coupe and S5 Cabriolet siblings).

           

I owned and loved a 1999 Audi A4, but I’m not a huge fan of the latest redesign: too big, too soft and too expensive. One 2009 A4 that I tested, with a mere 211 horsepower from a turbocharged 4-cylinder engine, topped $47,000 with a fistful of options. That’s a lot of money for a 4-cylinder anything.

          

Yet as we speak, I’m testing a brilliant blue S4, the A4’s high-performance cousin, and it seems like a totally different car. (I also drove the S4 on track in Napa and shot it though wine country.)

           

With 333 horsepower and 325 lb-ft of torque from a new, supercharged 3.0-liter six -- both surpassing the even 300/300 split of horsepower and torque in the BMW 335i -- the Audi hums from stoplight to 60 in 4.9 seconds. And from its fast-but-stealthy bodywork to its zestier interior and road-gobbling performance, the S4 makes the standard A4 look and feel like a grocery-getter. And despite bringing nearly 60 percent more horsepower to the party, at 333 versus 211, the S4 matches the A4’s 27 mpg on the highway.

           

Here’s the best part: The S4 I drove checked out at $52,000, only about $5,000 more than a tricked-out standard A4. Of course, the $46,725 base price is by no means cheap, but when considering the S4 (or, for that matter, the V10 R8 at three times its price), Type-A drivers should keep this mantra in mind: When it comes to these Audis, you really do get what you pay for.