"Aqui" is not Italian (it's Spanish if I am not mistaken). "Qui" and "qua" (never to be written with an accent!) are almost interchangeable. If anything, "qui" sounds more elegant than "qua" but this is just my opinion. There is actually a slight difference of meaning between the two: "qui" refers to this very specific place whereas "qua" is more general and includes "qui". But even native speakers don't pay attention to the difference.