More and more wealthy Americans are turning to the web to get their shopping done, but when it comes to luxury cars, they’d rather hit the showroom floor.

That’s the final word from a study conducted by the Luxury Institute, which found that, while shopping online for luxury goods is way up, only about one-fourth of us are comfortable buying our cars that way. The study, which surveyed households with an average net worth of $2.9 million, provides some interesting insight into high-end shopping.

Luxury shoppers appear to be much more at ease buying real estate or big-ticket jewelry items online; nearly 40 percent are content to do so. And nearly two-thirds of people with annual incomes of $150,000 or more are OK with buying fashion apparel or finding wealth advisors online. But when it comes to cars - well, the showroom experience just can’t be beat. Maybe it’s that new car smell.

“These highly tactile, big-ticket luxury items are generally better experienced rather than simply presented on a website,” explains Milton Pedraza, Luxury Institute CEO. However, that doesn’t mean luxury players don’t need a presence on the web.

Nearly two-thirds of all high-end shoppers go directly to the web to get more information on their purchases before they buy. So while today’s consumers are reluctant to make online purchases beyond $10,000 (the average comfort threshold for online purchases was about $3,294), the overall shift toward more online activity is making its way to higher end purchases.

So does that mean it’s only a matter of time before you’ll buy that new Aston Martin online? Time will tell. As Pedraza noted, it’s hard to truly get the “wow” effect from a web site; nothing beats walking into the showroom and driving off with a brand new steering wheel in your hands. This could be one experience that even technology can’t replicate - or replace.

Although women are buying about 60 percent of the cars out there today - and influencing the decision in 85 percent of all new car purchases, luxury auto manufacturers are still falling short when it comes to marketing.

“In terms of the luxury auto market, they could do much better at reaching women,” says Milton Pedraza, CEO of The Luxury Institute. “When you look at the ultra-luxury automakers, like Rolls-Royce, Ferrari and Maserati, they really have a long way to go.”

Pedraza says that a male-dominated industry has led to male-oriented marketing - even though the marketing firms behind the campaigns oftentimes are led by successful women.

“It’s an industry dominated by men, so they haven’t gotten the message that wealthy women are a force in their own right,” Pedraza points out. “You see it in every aspect, from the way the cars are marketed to the way women are treated in dealerships. A lot of them are not sensitive to the needs of a female driver and the buttons they need to press. Women are equally interested in [a car’s] performance, but also are drawn to the idea of achievement and rewarding yourself. This is what they luxury car manufacturers should be looking at.”

Those who do start paying attention to the fairer sex could find big rewards. With more and more women earning six and seven-figure incomes, they have the purchasing power that luxe auto manufacturers crave. Pedraza says that appealing to women’s more emotional side - as opposed to touting horsepower and speed - will be the key to success.

For proof of that, he points to Cadillac, which has found success in branding among women, thanks to some ads that show successful, attractive women enjoying their cars - and leaving male drivers in their dust.

“They’re showing women who are strong, powerful and functional,” says Pedraza. “But the one thing Cadillac still struggles with is identifying their market brand. On the one hand, they give us these great commercials with powerful, successful women, but then they also give us commercials featuring rappers, where women are used as a showpiece. In order to do better, they have to quit sending confusing signals.”

When brands like Aston Martin, Bentley and Ferrari refocus their campaigns, they could find a new following with a powerful, brand-loyal female marketplace.

“There’s a segment of women out there that like powerful cars, great styling and who love the driving experience,” Pedraza notes. “Luxury car brands need to understand that and speak to them as women. They need to be clear, distinct and respectful. But luxury car firms just haven’t gotten that yet.”

Apparently, Tom Cruise was right on the money when he uttered those much-quoted words: “Porsche. There is no substitute.” (Risky Business, 1983.)

According to a survey released earlier this month by New York City-based Luxury Institute, wealthy U.S. consumers still see Porsche as the world’s most prestigious luxury automotive brand. The poll was part of the 2008 Luxury Brand Status Index survey, and asked the opinions of 1,642 Americans with an average net worth of $3.7 million.

Porsche might have led the pack, but was followed closely by Lexus and Mercedes. Surprisingly, no Italian brands made the survey’s top 12. Other brands that did make the cut with consumers were (listed alphabetically) Acura, Audi, BMW, Cadillac, Infiniti, Jaguar, Land Rover, Lincoln and Volvo.

If you don’t have a Porsche of your own, and this has given you the need for speed, go visit my friend Ron at DFW Elite Auto Rental.com and he’ll hook you up with a Porsche for the day.