Have you looked at the Wipika rating ? also, try the http://www.kitesite.co.il
windrange section. should help but if I were you I'd be going for the 10 - 11.8 projected cos in Italy you will be fighting to get good winds for that size, also if you go bigger you can depower it for higher winds.
hope you are well. I just got the 17.5 ARX. see you in Vada ? maybe in Follonica on the sunday, give me a call.