Personally, I don't like when I only see one or two minor cf objects on a car - that screams to me, "I'm ballin on a budget." Generally, I don't really like cf hoods (stock-style or wild) on these cars either unless there are several other major aesthetic changes because they tend to stick out like a sore thumb on an otherwise stock-looking car. I do really like when owners of silver, red, yellow, blue, white, or any other light/bright colored WRX/STi have a cf hood with a scoop that's painted to match. I haven't seen that done on a black car, but I imagine it would be too subtle to really notice. If you want to try that, I bet it would still look cool though.
But in the end, you still have to do what you want. I applaud you for seeking opinions before doing something semi-major though. I assume you're just trying to feel out the waters before diving in?
07 WRX (Albins 5MT + Blouch 20G)
Jorge Carrillo Tuned (365 whp/340 wtq)