People that care about trade-in value or blue book value might as well get rid of their cars now. If you are thinking of selling the car when you purchase it, you are getting the wrong car. What is wrong with keeping a car for many years?
Adding a turbo does nothing for resale value, unless you will be selling it to someone that can appreciate the power and installation. A person that adds a turbo on their car does it for themself.
Now that this topic is very off-course.......