Since am in the Information Technology industry...I had initially known about CarsDirect from a company they had acquired called GreenLight.com which competes directly with CarsDirect.com.
I had built and design a DataCenter for GreenLight.com. Both uses massive search engines and have multiple contracts with dealers throughout the U.S. to market vehicles over the internet. The idear behind this internet business is the DotCom deliver the cars at your door via a flatbed truck, finance the car for you and provide the insurance for you right at their web-site. This is good for mainstream cars however because they have to resort to working on a resell contract basis with dealers....Cars like the MDX, the AUdi TT and what is consider high demand or "specialty" vehicle are difficult to source through Carsdirect.
Try buying a BMW Z8 or a Lates Range Rover or a Lamborghini Diablo.....heheheh...They cant help ya.