T think it's only worthy if your v8 STi is MY05 GDBE because it shares the same rear fender as the v9.
If yours is MY02-MY04 and you only convert the front to v9, it looks weird.
Since you just bought it, I suggest you spend the money to improve the handling and power. Once you like what you're driving, the looks really comes second.
Have you always wanted to try out some high speed driving on tyre screeching circuits, but just lack that bit of push to propel you into realizing your dreams?