Definetely have to agree with Nismoid. How much power are you making at the moment and how does the car feal? You are better off investing in a highflow or something in the likes of that to get you more power. Cams dont have to always give you more power, but usually just bring the power on better throughout the rev range. On a stock turbo set up the difference you will get from cams will be very minimal and honsetly you wont be happy with forking out a couple of grand with labour on a modification that isn't going to do much on your setup.
Go the turbo option at the moment, get all the necessary add-on modifactions to go without, then if you want to get more out of the setup go the cams.