Exactly. Anyway... why do people always say "I want 500BHP"? Do you know what that feels like? Have you seen the difference in 1/4 mile times between a 500BHP and a 550BHP supra?
What you should really be saying is: " I want a Supra that's fast off the lights and will beat most things up to the legal'ish speed limit" or "I want a drag Supra for Santa Pod and not worried about lag as I don't drive it everyday" or "I want a Supra that will be really fast around the track and nice and responsive, and quick down the straights". Then you can try build a car to match your needs.
Picking a power figure before you know anything about the cars is a little silly. Aim for what you're going to use it for, and then be happy with the dyno reading, whether it's 400BHP or 1000BHP.