Hiya it is all a question of taste really & how much u want to spend. Are you going to lower the car, because if not large wheels look silly with 2-3 inch above them, but again that is my taste. U could probably get away with 17" wheels without upseting the ride. U will only improve the handling as the larger tyres will have a smaller side wall to keep the rolling radius (RR) the same. If there is an Unicar showroom near u then pop in there as they have a cool little screen where u select ur car model then u can put different sets of wheels on it in like a virtual show room.