Why modify I4...

Hello all, im not here to make fun of you, i only have a couple of questions.

why do you guys buy hondas, (I4 engines, around 120-150 hp???), and modify them with thousands of dollars, when you could buy a, lets say, pontiac grand prix GTP (240 hp supercharged), and modify it with $500 and have 300 hp.

Is the I4 more reliable? or is it the challenge of trying to make a slow car go fast?

NOTE: i dont drive a grand prix GTP, i just used it for an example.