I checked out that middleman site.

Seems like just a way to get your $400.

Even if they negotiate for you, you still have to go check out the car and talk about the "extras". You have to like the car you are buying.

They want a credit card to put a "hold" on it before doing anything for you. If you opt to not give your card number right away they set up for their negotiator to call you. I am sure that call will be a high pressure sales pitch aimed at someone who has admitted they don't feel like a great negotiator and want someone to help them buy a car.

Seems like a definite way to part with $400.
Anyone use the site and have a positive experience?