17's will fit without too much hastle... however the ammount they scrape will depend very much on the ride height and the stiffness of the suspension... if you have a lowered ride height wil knackered standard susp then they will scrape like fook especially at the front...
My car (although a cab) has koni's all round set to hard and has a very low ride height.. this doesnt scrape but some 'modification' was required to the arches for the wheels to fit properly.
The key is how much do you want to lower the car...? if you dont want to lower it you would prob get away without any arch mods.. but it will look like a monster truck..
20-30mm then a little bit of modding is required or just set the suspension to hard and the lack of travel will mean the wheel wont catch the arch.
if you wish to go lower then you WILL have to modify the arch.. either by grinding it away or having it rolled...
which one you choose will depend on
A. how much of the rear arch is there in the first place
B. wether it is easy enough to get the bodykit off and re-fit it after rolling the arches..
CheeRs
Phil