First of all, before you go any bigger than 14, you want your car lowered by at least 35mm or it will look like a beach buggy. Secondly, if your planning on going for 17"s you will need uprated dampers coz the standard ones wont last 10 minutes, trust me, been there done that, got the t-shirt
For 17's you will need 40mm profile tyres which are expensive and you will still get some rubbing going over bumps etc. Also, the acceleration of your car will be affected along with ride quality and steering.
16"s, again lowered + uprated shocks. Can go up to 45mm with some slight rubbing. Poor ride quality, harder steering, slower off the mark
15"s ideal compromise between style and spped, still need it lowered, will get away without shocks, ride quality a bit better than 16/17". Overall better choice
However, i got 16"s on mine n am happy with them n there have been a few people with 17"s on theres, all depends weather your prepared to sacrifice a bit of crappy performance for the looks and if your not interested in the performance go for 17"s otherwise i would advise 15"s