As far as Mod list decreasing the value, this is very misunderstood. To a dealer a large mod list, aftermarket tuning, turbo ect this decreases value to a dealer who would have to imply reliability and some type of a warranty in most states. But on that note let me pose the question.
When you buy a race car with a $10,000 motor, stripped out with a roll cage do you use KBB?
If the work was done well, by a verifiable and reputable shop the car is worth the value that a buyer would pay for it. If you wanted to buy a car from ESX tuning you would pay $45,000 as opposed to its blue book value of $31,000 new. But for example let me show you what I would ask for my car.
2005 Legacy GT 71,000 miles, VF 52 turbo, DW265lph fuel pump, Perrin top mount intercooler, Perrin BOV, Perrin dual cat back, Perrin uppipe, Perrin catch can, Perrin inlet pipe, Perrin ram air