Factory, or Improved Horsepower?

As long as there have been sports cars and muscle cars people have tried to increase the HP they put out. There are slight increased like adding fuel additives, or air filter/path changes. Then there are the modest mods: ECU upgrades, exhaust etcetera. Then you have the loonies.. There is a guy at my work that had a perfectly nice Pontiac GTO and then swapped out the stock engine and replaced it with a huge performance crate motor from GM.. it took the dealer a week to get it in and tuned to the point that he could drive it and it is still extremely hard to drive. There is some tuning left to do so that he does not stall at stop lights and the thing is seriously loud and very fast! I am not sure it is worth it though. All that effort and you have a daily driver that can't be driven daily anymore. That is one example, but you see it all over the place, supercharged vw's or bolt on turbos where they don't belong. I know cars are not investments, but they don't have to be total wastes of cash.. I mean who wants to buy someone's supercharged Toyota Camry? No one that's who. Well maybe a kid somewhere, but they usually don't have any money anyway.
The point is that if you are looking to increase your HP / Thrill factor, why not spare your current ride, get a decent sale out of it, throw in what you were going to spend on upgrades and get a car that is more powerful as sold by the dealer. Used or new it would make more sense. Then after enjoying that car for a while you can sell it for another faster car or for something else entirely like a minivan (ack, I just vomited in my mouth a little).