The Luxury Institute, which bills itself as "the uniquely impartial, independent and objective ratings and research organization that is the global voice of the high net-worth consumer", has conducted a survey of the wealthy and found that Porsche is the "best of the best" when it comes to luxury car brands.

http://rumors.automobilemag.com/6507124/news/the-luxury-institute-rates-porsche-as-best-luxury-brand/index.html