All the advice people have given in this thread is excellent. Someone mentioned Pro Team Corvettes, and, while I didn't buy a car from them I went there from Houston to look at a car, and was given the biggest bunch of b.s. you could imagine. My opinion of many of these dealers is that they simply buy cars which look shiny or do a cheapy in-house paint job, buff them up, then turn around and try and sell them at the highest price that they see that particular make or model going for elsewhere, even if the car is mechanically shot and dangerous to drive. Also, many of them flat out lie, and I think we have all gone through the shock of shaking our heads and not believing that people could lie like this. Amazing.
I would also like to put in a plug for ebay. Ebay has added a transparency to the market which is great, as there you can see what people are really willing to pay for a car if you look at things like the bid history. This gets around sellers saying things like "you better act now, or 5 other people will pay my price...., the phone has been ringing off the hook etc" You also notice trends (e.g., in Corvettes, the incredible effect of originality and mileage on price--great for people like me who want to drive a real car, not show it)There is a great magazine called Sports Car Market, and they have noted that Ebay has totally revolutionized the market for classic and enthusiast cars, regardless of whether you are talking about run of the mill vehicles or rare or exotic cars. Ebay is giving all the auction houses a real run for the money. It's great!
--Chris Kennedy